Optimized construction method for sand control completion of ultra-deep water ultra-shallow gas low-temperature reservoirs by coating sand filling

Abstract

This invention belongs to the field of oil and gas engineering technology, specifically relating to an optimized construction method for sand control and well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs using coated sand filling. The method includes: S1, a screen-tube coated sand circulation filling construction method for ultra-deepwater and ultra-shallow gas cryogenic reservoirs that ensures the consolidation of the coated sand; S2, a method for designing the temperature and liquid volume of the near-wellbore reservoir during the heat treatment stage before circulation filling in ultra-deepwater and ultra-shallow gas cryogenic reservoirs; and S3, a method for designing the hot liquid coated sand gravel filling and displacement liquid volume in ultra-deepwater and ultra-shallow gas cryogenic reservoirs. This invention can successfully apply the coated sand filling and well completion technology, which was originally unusable in ultra-deepwater and ultra-shallow gas cryogenic reservoirs due to insufficient consolidation conditions, to ultra-deepwater and ultra-shallow gas cryogenic reservoirs. Simultaneously, it does not increase the complexity of traditional circulation filling construction processes, is simple and easy to implement, highly operable, and requires less time on ultra-deepwater offshore platforms, thus saving construction costs.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas engineering technology, specifically relating to an optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs. Background Technology

[0002] Deep-seated (including deep-earth and deep-water) oil and gas resource development is a major area of ​​oil and gas energy development in my country, among which ultra-deep-water and ultra-shallow gas reservoirs are an important type of deep-seated oil and gas resource. my country has currently preliminarily proven geological reserves of ultra-deep-water and ultra-shallow natural gas reaching hundreds of billions of cubic meters. However, ultra-deep-water and ultra-shallow gas reservoirs have water depths of 1500-1700 meters and are buried approximately 150-300 meters below the seabed, characterized by shallow burial, low temperatures (approximately 15°C), and weak cementation. These reservoirs are weakly diagenetic or even non-diagenetic, making them prone to reservoir structural instability and sand production during extraction. Therefore, for ultra-deep-water and ultra-shallow gas reservoirs, sand control completion technology not only needs to achieve efficient sand control and ensure gas well productivity, but also needs reliable wellbore support capacity and long-term service stability, placing extremely high demands on process applicability and engineering feasibility.

[0003] Screen-filled gravel packing is the dominant technology for sand control completion in offshore horizontal wells, while coated sand possesses self-consolidating properties under bottomhole conditions. Combining screen-filled gravel packing and coated sand creates a high-strength, consolidated sand-blocking and supporting barrier in the screen and wellbore annulus, effectively addressing the core requirements of sand control completion in ultra-deepwater and ultra-shallow gas wells. This is a highly promising sand control completion technology. However, this technology still faces the following key challenges:

[0004] (1) The temperature of ultra-deep water and ultra-shallow gas reservoirs in my country is only about 15℃, while the lowest solidification temperature of coated sand at present is 18-20℃. The higher the ambient temperature, the easier it is for coated sand to solidify; conversely, the lower the temperature, the more difficult it is to solidify. As a result, the existing coated sand cannot directly meet the sand control requirements of ultra-deep water and ultra-shallow gas low temperature reservoirs.

[0005] (2) The lack of operable technical solutions, optimized design methods, and implementation processes for sand control completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs means that there is currently no clearly defined and feasible sand control completion technology. For example, Chinese patent document CN110593810A proposes a method for heating and solidifying tubing with circulating hot fluid to promote the solidification of artificial well walls. This method creates a new artificial well wall at the damaged section of the screen pipe, eliminating the need to determine the location of the screen pipe damage and enabling rapid repair of damaged screen pipes. However, this method is time-consuming, consumes a large amount of fluid, occupies a long time on the deepwater platform, and is costly. Furthermore, this method does not provide specific temperature and fluid volume design methods, making it difficult to implement.

[0006] Chinese patent document CN120719964A discloses a method for identifying and evaluating the instability modes of coated sand layers in air-storage wells. The method includes: Step 1, determining the initial state parameters of the evaluation object and determining the flow rate in the experimental evaluation based on similarity criteria; Step 2, collecting parameters at both ends of the coated sand filling layer during the experiment, classifying the instability failure modes of the coated sand filling layer in air-storage wells under alternating injection and production conditions, and identifying the instability failure modes; Step 3, calculating various indicators based on the collected parameters; and Step 4, conducting production control and evaluating the coated sand filling layer based on the indicator calculation results. However, this method has clear limitations in its applicability. It is only applicable to conventional air-storage wells, primarily focusing on stability analysis and pattern recognition under existing wellbore conditions. It falls under the category of post-hoc identification and risk assessment, and does not consider the impact of low reservoir temperature on coated sand consolidation. Therefore, it cannot meet the sand control completion requirements of ultra-deepwater and ultra-shallow gas reservoirs and is difficult to apply to engineering practices for such reservoirs.

[0007] In summary, there is an urgent need for an optimized construction method for sand-filling and sand-control completion of cryogenic reservoirs in ultra-deepwater and ultra-shallow gas reservoirs. This method would address technical challenges such as difficulties in cryogenic consolidation, lack of system design, and mismatched construction processes, thereby meeting the needs for safe and efficient development of ultra-deepwater and ultra-shallow gas reservoirs. Summary of the Invention

[0008] To address the aforementioned issues, this invention proposes an optimized construction method for sand control and well completion in ultra-deepwater and ultra-shallow gas low-temperature reservoirs. This method overcomes the bottleneck problem that sand control technology with self-consolidation characteristics is difficult to apply to ultra-deepwater and ultra-shallow gas reservoirs due to insufficient temperature conditions. Simultaneously, it provides a reliable sand control and well completion technology and its optimized implementation method for low-temperature, weakly-unconsolidated reservoirs in ultra-deepwater and ultra-shallow gas reservoirs, resolving reservoir collapse instability and sand production issues during the development of such reservoirs, and achieving long-term, efficient production.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] Optimized construction methods for sand-filling and sand-control completion of ultra-deepwater and ultra-shallow gas cryogenic reservoirs include:

[0011] S1. A screen-tube coated sand circulation backfilling construction method for ultra-deep water and ultra-shallow gas cryogenic reservoirs that ensures the consolidation of coated sand:

[0012] Heat pretreatment fluid is pumped into the annulus of the screen sleeve in the circulation channel to raise the original temperature of the reservoir near the well to the temperature range where the coated sand can solidify; then heat-carrying sand fluid is pumped into the annulus of the screen sleeve for circulation filling; after filling, sand-free displacement fluid is pumped into the annulus of the screen sleeve to fully replace the residual heat-carrying sand fluid in the annulus of the screen sleeve and the screen tube; after replacement, the circulation channel is closed and the construction is completed.

[0013] Preferably, the near-wellbore area refers to the formation area extending radially from the horizontal wellbore axis into the formation within the effective heating radius of the near-wellbore reservoir.

[0014] Preferably, in step S1, the original temperature of the reservoir in the near-well area is raised to the minimum consolidation temperature of the coated sand.

[0015] More preferably, step S1 specifically includes:

[0016] a. Heat treatment reservoir stage: After the completion string is run into the target well section and the structure is sealed, the heat pretreatment fluid is pumped into the screen pipe through the heat-insulated tubing or a special circulation string, and enters the screen sleeve annulus through the screen holes of the screen pipe to raise the original temperature of the reservoir in the near-well area to the minimum consolidation temperature of the coated sand.

[0017] b. Heat-carrying sand fluid circulation and filling stage: After the heat treatment reservoir stage is completed, heat-carrying sand fluid containing coated sand is pumped into the screen pipe through the heat-insulated oil pipe or a special circulation string. The heat-carrying sand fluid carries the coated sand to the screen sleeve annulus and gradually deposits, accumulates and fills the screen sleeve annulus and near-wellbore void under the action of circulation flow, forming a continuous and uniform particle accumulation layer.

[0018] c. Replacement stage: After the heat-carrying sand fluid circulation and filling stage is completed, sand-free replacement fluid is pumped into the screen pipe through the heat-insulated oil pipe or a special circulation string to fully replace the residual heat-carrying sand fluid inside the screen pipe and the screen sleeve annulus, so as to prevent unconsolidated sand particles left in the wellbore from affecting subsequent production.

[0019] d. After the replacement phase is completed, the circulation channel is closed and the construction is finished.

[0020] Preferably, the optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs further includes:

[0021] S2. A method for designing the temperature and fluid volume of the near-wellbore reservoir during the pre-filling heat treatment stage of ultra-deepwater and ultra-shallow gas cryogenic reservoirs. This method designs the parameters of the heat pretreatment fluid based on the cryogenic consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation, and optimizes the on-site construction parameters based on the designed parameters. The parameters of the heat pretreatment fluid include the inlet temperature T. p , heat pretreatment liquid pump injection and discharge rate q p With the continuous injection time t of the heat pretreatment liquid p .

[0022] More preferably, the parameter design of the thermal pretreatment fluid based on the low-temperature consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation is specifically as follows:

[0023] a. Determine the effective heating radius r of the near-wellbore reservoir based on the critical temperature propagation condition. eOr the continuous injection time of the heat pretreatment liquid t p ;

[0024] b. Based on the effective heating radius of the near-wellbore reservoir, calculate the heat Q required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand. r ;

[0025] c. The amount of heat Q required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand. r and the continuous injection time t of the heat pretreatment liquid p Calculate the inlet temperature T of the heat pretreatment liquid. p , heat pretreatment liquid pump injection and discharge rate q p .

[0026] More preferably, in step a, when the minimum liquid volume principle is met, i.e., the effective heating radius of the near-wellbore reservoir is equal to the wellbore radius and is a known quantity, the continuous injection time t of the thermal pretreatment fluid is calculated using the effective heating radius of the near-wellbore reservoir. p When the heat pretreatment liquid is continuously injected for time t p When the quantity is known, the effective heating radius of the near-wellbore reservoir can be calculated, as follows:

[0027] The critical temperature propagation condition is as follows:

[0028] (1)

[0029] In the formula, T c —Minimum consolidation temperature of the coated sand, °C; T0—Original reservoir temperature, °C; T max —Maximum allowable temperature for coating sand, °C; erfc()—Complementary error function, which can be calculated by looking up a table in engineering; r e —Effective heating radius of the near-wellbore reservoir, m; α—Formation thermal diffusivity, m 2 / s;t p —Continuous injection time of heat pretreatment fluid, s;

[0030] The effective heating radius of the near-wellbore reservoir, based on the radial transient heat conduction theory, is determined under conditions of continuous injection of a constant-temperature pretreatment fluid for a duration of t. p Under known conditions, the near-wellbore temperature influence range, i.e., the effective heating radius of the near-wellbore reservoir, can be expressed using a simplified engineering expression:

[0031] (2)

[0032] (3)

[0033] (4)

[0034] In the formula, ξ—complementary error coefficient, dimensionless; λ—formation thermal conductivity, W / (m·℃); ρ f —Effective density of the formation, kg / m³ 3 ;c f —Equivalent specific heat capacity of the formation, J / (kg·℃);

[0035] If the minimum liquid volume principle is satisfied, then r e =r w According to equation (4), the continuous injection time t of the heat pretreatment liquid can be calculated. p :

[0036] (5)

[0037] In the formula, r w —Wellbore radius, m;

[0038] The amount of heat required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand, as described in step b:

[0039] Simplifying the near-wellbore region into a homogeneous isotropic cylindrical formation unit, neglecting the axial temperature gradient and considering only radial heat conduction, the near-wellbore region temperature increases from the original reservoir temperature T0 to the minimum consolidation temperature T of the coated sand. c The total calories required are:

[0040] (6)

[0041] In the formula, Q r —The amount of heat required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand, in J; L—Effective length of the well section, in m; —Reservoir porosity, %

[0042] Step c includes:

[0043] Calculate the heating heat after heat loss correction:

[0044] Considering the heat transfer due to the temperature difference between the wellbore and the formation, as well as the heat dissipation during the circulation process, and introducing a comprehensive thermal efficiency coefficient, the heating heat after heat loss correction is:

[0045] (7)

[0046] In the formula, Q is the heating heat after heat loss correction, in J; η is the overall thermal efficiency coefficient, dimensionless, with a recommended value of 0.6-0.8;

[0047] Calculate the injection volume of the heat pretreatment fluid:

[0048] The effective heat that a unit volume of pretreatment liquid can provide is:

[0049] (8)

[0050] In the formula, Q p —Effective heat per unit volume of pretreated liquid, J / m³ 3 ;ρ p —Density of the heat pretreatment solution, kg / m³ 3 ;c p —Specific heat capacity of the heat pretreatment liquid, J / (kg·℃); T p —Inlet temperature of the heat pretreatment liquid, °C.

[0051] The minimum injection volume required for the heat pretreatment fluid is:

[0052] (9)

[0053] In the formula, V p —Minimum injection volume of heat pretreatment fluid, m 3 ;q p —Preheating pretreatment liquid pump injection / discharge rate, m 3 / s.

[0054] If the inlet temperature T of the heat pretreatment liquid is known p The injection and discharge rate q of the heat pretreatment liquid pump is calculated according to formula (10). p :

[0055] (10)

[0056] If the injection / discharge rate q of the heat pretreatment liquid pump is known... p The inlet temperature T of the heat pretreatment liquid is calculated according to formula (11). p :

[0057] (11)

[0058] Furthermore, the optimization of on-site construction parameters based on design parameters shall be carried out according to the following priority principles:

[0059] a. Temperature Priority Principle: The inlet temperature of the heat pretreatment fluid should be maintained according to the following inequality to compensate for heat transfer losses in the wellbore:

[0060] (12)

[0061] b. Minimum Liquid Volume Principle: Select the minimum injection volume of the heat pretreatment liquid while meeting the following principles:

[0062] (13)

[0063] c. Construction time constraint principle: By increasing the injection and discharge rate q of the heat pretreatment liquid pump. p Or the inlet temperature T of the heat pretreatment liquid pThe heat pretreatment liquid is continuously injected for a time t. p The operation should be controlled within the acceptable operating window of the deep-water platform, depending on the specific on-site operating conditions.

[0064] Preferably, the optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs further includes:

[0065] S3. Design method for hydrothermal coating, gravel filling, and displacement fluid volume of cryogenic reservoirs in ultra-deep water and ultra-shallow gas layers:

[0066] S31. Establish a quantitative analytical relationship between the minimum inlet temperature of the thermally carried sand slurry, the duration of circulating filling, and the minimum displacement of circulating filling, in order to achieve the minimum inlet temperature T of the thermally carried sand slurry. s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The coordinated design ensures that the near-wellbore temperature remains at or above the minimum consolidation temperature of the coated sand during the hot-carrying sand circulation filling process, and remains above the minimum consolidation temperature of the coated sand for a duration of t. s Internal consolidation is completed;

[0067] S32. Calculate the displacement liquid volume to achieve full replacement of the residual heat-carrying sand liquid in the annulus of the screen sleeve and inside the screen tube.

[0068] More preferably, in step S31, a quantitative analytical relationship is established between the minimum inlet temperature of the thermally carried sand slurry, the duration of circulating filling, and the minimum discharge rate of circulating filling, so as to achieve the minimum inlet temperature T of the thermally carried sand slurry. s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The collaborative design ensures that the near-wellbore temperature remains within the solidification range of the coated sand during the hot-carrying sand fluid circulation filling process and for a duration of t. s Internal consolidation is completed;

[0069] More preferably, in step S31, the minimum inlet temperature T of the heat-carrying sand fluid is calculated based on the transient radial heat conduction analytical solution. s Based on the lowest inlet temperature T of the thermally carried sand slurry s Given the total heat constraint of the heat-carrying sand liquid, the minimum displacement q for cyclic filling is obtained. s To achieve the lowest inlet temperature T of the thermally carried sand slurry s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The collaborative design, and based on the cycle filling duration t s and the minimum displacement q of the cyclic filling s Calculate the volume of liquid used for thermally carried sand circulation filling.

[0070] More preferably, step S31 specifically includes:

[0071] First, calculate the inlet temperature of the heat-carrying sand fluid circulation filling:

[0072] During the hot-carrying sand fluid circulation filling process, the temperature at the wellbore must always meet the following constraints:

[0073] (14)

[0074] in, This refers to the temperature at the wellbore wall at time t;

[0075] Based on the analytical solution of transient radial heat conduction, the temperature distribution of the reservoir at radius r at time t can be obtained:

[0076] (15)

[0077] In the formula, —Temperature of the reservoir at radius r at time t, where r is the radius extending from the wellbore axis towards the formation; T is the inlet temperature of the heat-carrying sand fluid circulation filling, in °C; t s —Duration of cyclic filling, s.

[0078] At the well wall, r=r w The lowest inlet temperature of the heat-carrying sand fluid was obtained. :

[0079] (16)

[0080] Secondly, calculate the minimum displacement for cyclic filling:

[0081] To ensure that during the cyclic filling duration t s Within the wellbore region, the temperature must be maintained at or above the minimum consolidation temperature of the coated sand. The total heat provided by the heat-carrying sand fluid must meet the energy requirements for formation heating. The constraints are as follows:

[0082] (17)

[0083] Based on formulas (16) and (17), the minimum displacement for cyclic filling can be obtained:

[0084] (18)

[0085] In the formula, q s —Minimum displacement for cyclic filling, m 3 / s;r c —Design consolidation control radius, m; ρ s —Density of thermally saturated sand, kg / m³ 3 ;c s—Specific heat capacity of heat-carrying sand liquid, J / (kg·℃);

[0086] Calculate the volume of liquid used for thermally carried sand circulation filling:

[0087] (19)

[0088] In the formula, V s —The volume of liquid filled by the heat-carrying sand circulation system, in m 3 .

[0089] According to equations (16) and (18), a given T can be achieved. s t s q s Any one of the three parameters is used to calculate the other two parameters, thus achieving the minimum inlet temperature T of the thermally carried sand fluid. s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s Collaborative design.

[0090] Preferably, the displacement liquid volume in step S32 is calculated according to the following formula:

[0091] (20)

[0092] In the formula, V d —Displacement fluid volume, m 3 ; β—Construction safety margin coefficient, dimensionless.

[0093] Compared with the prior art, the present invention has the following beneficial effects:

[0094] (1) The screen-tube coated sand circulation filling construction method of the present invention, which ensures the consolidation of coated sand in ultra-deepwater and ultra-shallow gas cryogenic reservoirs, solves the problem that existing coated sand cannot be consolidated in ultra-deepwater and ultra-shallow gas cryogenic reservoirs, thus making it unusable. It can successfully apply the coated sand filling sand control completion process, which originally could not be applied in ultra-deepwater and ultra-shallow gas cryogenic reservoirs due to insufficient consolidation conditions, to ultra-deepwater and ultra-shallow gas cryogenic reservoirs. Not only does it play a sand control role, but after the coated filling layer consolidates, it forms a high-strength barrier that can support the well wall of ultra-shallow reservoirs and prevent collapse.

[0095] (2) The temperature and liquid volume design method for the near-wellbore reservoir during the pre-heat treatment stage of the cyclic filling proposed in this invention designs the parameters of the pre-treatment fluid based on the low-temperature consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation, and optimizes the on-site construction parameters based on the designed parameters. This method can stably raise the near-wellbore reservoir temperature to the range where the coated sand can be consolidated, minimize the injected liquid volume and heat energy consumption, and provide a reliable thermodynamic basis for the subsequent hot liquid coated sand gravel filling and displacement liquid volume design method.

[0096] (3) The coating gravel filling and displacement fluid volume design method proposed in this invention establishes a quantitative analytical relationship between the minimum inlet temperature of the heat-carrying sand fluid, the duration of the circulating filling, and the minimum discharge of the circulating filling, so as to achieve the coordinated design of the minimum inlet temperature of the heat-carrying sand fluid, the duration of the circulating filling, and the minimum discharge of the circulating filling, thereby minimizing ineffective heat consumption and excess treatment fluid injection, avoiding excessive thermal disturbance and pollution to the reservoir, and thus achieving optimized control of construction costs and energy consumption while ensuring the sand control and wellbore support effects.

[0097] (4) The process proposed in this invention, which involves first pumping in a thermal pretreatment liquid and then using a thermally carried sand liquid for coating and cyclic filling, does not increase the complexity of the traditional cyclic filling construction process. It is simple, easy to implement, and highly operable. According to the method of this invention, the operation time is generally no more than 12 hours, while the operation time of the prior art is usually more than one day. This shows that the method of this invention occupies less operation time on ultra-deepwater marine platforms and saves construction costs. Attached Figure Description

[0098] Figure 1 This is a schematic diagram of the heat treatment reservoir stage of the screen tube coated sand circulation filling construction method for ultra-deep water and ultra-shallow gas cryogenic reservoirs, which can ensure the consolidation of coated sand.

[0099] Figure 2 This is a schematic diagram of the thermally carried sand liquid circulation filling stage of the screen tube coated sand circulation filling construction method for ultra-deep water and ultra-shallow gas cryogenic reservoirs in Embodiment 1 of the present invention, which can ensure the consolidation of coated sand.

[0100] Figure 3 This is a schematic diagram of the replacement stage of the screen tube coated sand circulation filling construction method for ultra-deep water and ultra-shallow gas cryogenic reservoirs in Embodiment 1 of the present invention, which can ensure the consolidation of coated sand.

[0101] Figure 4 This is a schematic diagram of the axial temperature control of the horizontal wellbore in the optimized construction method of sand-filling and sand-controlling well completion for ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to Embodiment 1 of the present invention.

[0102] Figure 5 This is a schematic diagram of temperature control during gravel filling operations in the optimized construction method for sand control and well completion of ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to Embodiment 1 of the present invention. Detailed Implementation

[0103] In the embodiments of the present invention, both the heat pretreatment liquid and the sand-free displacement liquid used are heated water.

[0104] Example 1

[0105] Optimized construction methods for sand-filling and sand-control completion of ultra-deepwater and ultra-shallow gas cryogenic reservoirs include:

[0106] S1. A screen-tube coated sand circulation backfilling construction method for ultra-deep water and ultra-shallow gas cryogenic reservoirs that ensures the consolidation of coated sand:

[0107] Heat pretreatment fluid is pumped into the annulus of the screen sleeve in the circulation channel to raise the original temperature of the reservoir near the well to the temperature range where the coated sand can solidify; then heat-carrying sand fluid is pumped into the annulus of the screen sleeve for circulation filling; after filling, sand-free displacement fluid is pumped into the annulus of the screen sleeve to fully replace the residual heat-carrying sand fluid in the screen tube and the annulus of the screen sleeve; after replacement, the circulation channel is closed and the construction is completed.

[0108] To address the low-temperature, weakly cemented, and easily unstable characteristics of ultra-deepwater and ultra-shallow gas reservoirs, this embodiment constructs a screen-coated sand circulating filling construction method with "heat-treated reservoir - circulating filling - displacement" as the core process. During construction, a heat pretreatment fluid is first pumped into the annulus of the screen casing to raise the original temperature of the reservoir near the wellbore to the range where the coated sand can solidify. Then, a heat-carrying sand fluid is used for circulating filling, allowing the coated sand to form a continuous and dense filling structure in the annulus of the screen casing and the near-wellbore area. This structure achieves stable consolidation during the subsequent displacement process, ultimately forming a coated sand consolidation sand barrier around the wellbore that combines high-strength support capacity with stable seepage channels. This meets the engineering requirements for long-term sand control and structural stability in ultra-shallow, weakly-uncemented reservoirs.

[0109] Specifically, the construction method for the screen-tube coated sand circulation filling consolidation sand control completion technology is carried out in the following order: "heat treatment of the reservoir - heat-carrying sand fluid circulation filling - displacement - closing the circulation channel and ending the construction":

[0110] like Figure 1 , Figure 2 , Figure 3 As shown, the target operating reservoir, from top to bottom, consists of an ultra-deep water layer, a mud layer, an ultra-shallow gas layer, and a bottom layer. The target reservoir is an ultra-shallow gas layer. The downhole tubing system mainly includes casing, screen pipe, and flushing pipe.

[0111] Specifically, the near-wellbore area refers to the formation area extending radially from the horizontal wellbore axis to the effective heating radius of the near-wellbore reservoir; the temperature range in which the coated sand can be consolidated is 20-90℃.

[0112] Specifically, the circulation channel is a closed circulation flow channel formed by a heat-insulated oil pipe or a dedicated circulation tubing string and the annulus of the screen sleeve:

[0113] In this embodiment, the thermal pretreatment fluid / thermal sand-carrying fluid / sand-free displacement fluid is pumped in through the insulated tubing or a dedicated circulation string, enters the annulus of the screen sleeve through the screen holes of the screen pipe, exchanges heat with the near-well area, and then flows back out through the flush pipe and the diversion device, and then enters the annulus formed by the wellbore and the insulated tubing (or dedicated circulation string) and flows out of the wellhead.

[0114] a. Heat treatment of reservoir stage: such as Figure 1 As shown, Figure 1 This diagram illustrates the principle of the heat treatment stage of the screen-tube coated sand circulation filling construction method. After the completion string is run into the target well section and the structure is sealed, a constant-temperature pretreatment fluid with stable heat transfer properties is pumped into the screen tube at a constant flow rate through insulated tubing or a dedicated circulation string. The fluid then enters the annulus through the screen holes, gradually increasing the near-wellbore temperature. This allows the formation within the effective heating radius of the near-wellbore reservoir to smoothly transition from the original reservoir temperature T0 to the minimum consolidation temperature of the coated sand, ensuring spatial uniformity and temporal stability. This method not only creates an effective heat-affected zone in the near-wellbore area but also inhibits excessive heat loss to the far-field formations, thus providing a stable thermodynamic environment for subsequent heat-carrying sand fluid circulation filling.

[0115] b. Thermally carried sand molten material circulation filling stage: such as Figure 2 As shown, Figure 2 This diagram illustrates the principle of the heat-carrying sand fluid circulation filling stage in the screen tube coated sand circulation filling construction method. After the heat treatment of the reservoir stage, the heat-carrying sand fluid is pumped in. The heat-carrying sand fluid containing coated sand is continuously pumped into the screen sleeve annulus through insulated tubing or a dedicated circulation string. Under the action of circulation flow, it gradually deposits, accumulates, and fills the screen sleeve annulus and near-wellbore voids, forming a continuous and uniform particle accumulation layer. By controlling the duration of circulation filling and the sand content of the returned fluid, until the annulus and near-wellbore void areas reach the designed filling density, a filling layer with both sand-blocking capacity and seepage channel stability is constructed (the control of the sand content of the returned fluid and the designed filling density are achievable by those skilled in the art and are not the content to be protected by this invention).

[0116] The screen-coated sand circulation packing consolidation sand control completion technology, based on the conventional screen-coated gravel packing completion structure for offshore horizontal wells, uses resin-coated quartz sand instead of ordinary gravel as the main packing medium (not the subject of this invention). This forms a thermally solidifiable particle skeleton structure in the annulus and near-wellbore void. When the original reservoir temperature in the near-wellbore area is raised to the minimum consolidation temperature of the coated sand, the coating resin undergoes a cross-linking reaction, transforming discrete particles into a solidified body with overall mechanical strength. This forms a continuous and stable artificial support layer and sand barrier around the wellbore. The consolidated packing layer simultaneously performs three functions: wellbore mechanical support, sand filtration, and seepage channel maintenance. For wellbore mechanical support, the coated sand packing layer inhibits collapse or shear failure of ultra-shallow, weakly cemented formations under production pressure differentials. For sand filtration, the consolidated particle skeleton forms stable filtration channels, preventing fine formation sand from entering the wellbore. For seepage channel maintenance, it maintains high effective permeability while ensuring structural strength, reducing the impact on gas well productivity.

[0117] c. Replacement stage: such as Figure 3 As shown, Figure 3 This diagram illustrates the principle of the replacement stage in the screen pipe coating and circulating filling construction method. After the hot-carrying sand fluid is circulated and filled, sand-free replacement fluid is pumped into the screen pipe through insulated tubing or a dedicated circulation string. This fully replaces the residual hot-carrying sand fluid inside the screen pipe and the annulus of the screen sleeve, preventing unconsolidated sand particles in the wellbore from affecting subsequent production. Simultaneously, the smooth fluid replacement process helps redistribute the fluid pressure and particle stress state within the filling zone, suppressing the risk of local structural loosening or collapse, thereby improving the stability and integrity of the overall filling structure.

[0118] d. Construction phase ends after closing the circulation channel: After the displacement is completed, the construction ends after closing the circulation channel, ultimately transforming the filling layer from a loose accumulation to a continuous consolidated skeleton. A consolidated support-sand control composite structure with long-term mechanical stability and effective sand-blocking capability is formed in the annulus of the screen sleeve and near the wellbore.

[0119] The characteristics and advantages of the aforementioned screen-tube coated sand circulation filling consolidation sand control completion technology are as follows: This technology targets ultra-deepwater and ultra-shallow gas reservoirs with low temperatures, weak-to-uncemented conditions, and high instability. Through coordinated control of the reservoir heat treatment stage and the heat-carrying sand fluid circulation filling stage, it achieves reliable consolidation of the coated sand in an environment with temperatures lower than those suitable for conventional consolidation. This fundamentally overcomes the technical bottleneck of traditional coated sand technology being limited by formation temperature. Simultaneously, the resulting continuous, integral consolidation filling layer combines multiple functions, including wellbore mechanical support, effective fine sand control, and efficient seepage maintenance. This minimizes the adverse impact on gas well productivity while ensuring sand control reliability. Furthermore, this process is highly compatible with conventional circulation filling operations in terms of construction flow, without significantly increasing the complexity of downhole tools or platform operation time. It boasts advantages such as strong engineering feasibility, low construction risk, high thermal energy utilization efficiency, and controllable overall costs, making it suitable for the long-term stable sand control completion needs of ultra-deepwater and ultra-shallow gas reservoirs with low temperatures.

[0120] S2. A method for designing the temperature and liquid volume of the near-wellbore reservoir during the pre-heat treatment stage of ultra-deepwater and ultra-shallow gas cryogenic reservoirs before cyclic filling. This method designs the parameters of the pre-treatment fluid based on the cryogenic consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation, and optimizes the on-site construction parameters based on the designed parameters. Figure 1 As shown, the parameters of the thermal pretreatment fluid include the inlet temperature T of the thermal pretreatment fluid. p , heat pretreatment liquid pump injection and discharge rate q p With the continuous injection time t of the heat pretreatment liquid p .

[0121] Specifically, based on the low-temperature consolidation kinetics and the radial transient heat conduction characteristics of the near-wellbore formation, a temperature-time-volume coupled design method for hot fluid pretreatment before cyclic filling is established. By determining the effective heating radius of the near-wellbore reservoir, the amount of heat required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand, and the comprehensive thermal efficiency coefficient η, the inlet temperature T of the pretreatment fluid can be quickly calculated under given reservoir and coated sand properties. p , heat pretreatment liquid pump injection and discharge rate q p Minimum injection volume of heat pretreatment fluid and continuous injection time t of heat pretreatment fluid p Based on this, engineering optimization principles are proposed. This method facilitates the optimization of parameter ratios, costs, and energy consumption on-site within a limited operating window, and can also serve as the thermodynamic basis for subsequent hot-carrying sand cyclic filling design.

[0122] The parameter design of the thermal pretreatment fluid based on the low-temperature consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation is as follows:

[0123] a. Determine the effective heating radius r of the near-wellbore reservoir based on the critical temperature propagation condition. e Or the continuous injection time of the heat pretreatment liquid t p ;

[0124] When the minimum liquid volume principle is met, i.e., the effective heating radius of the near-wellbore reservoir is equal to the wellbore radius and is a known quantity, the continuous injection time t of the thermal pretreatment fluid can be calculated using the effective heating radius of the near-wellbore reservoir. p When the heat pretreatment liquid is continuously injected for time t p When the quantity is known, the effective heating radius of the near-wellbore reservoir can be calculated, as follows:

[0125] Continuous injection time t of heat pretreatment liquid p The time required for the heat to rise to the target temperature is determined. In actual construction operations, to simplify calculations and facilitate solutions, it can be approximated that when the heat front just reaches the target radius, the minimum consolidation temperature of the coating sand can be reached within the shortest injection time, i.e., when r=r e The temperature reached T for the first time c In the early heat transfer stage near the wellbore, the radial temperature gradient is concentrated in a thin layer near the wellbore. At this time, the radial heat conduction equation can be equivalent to a semi-infinite one-dimensional unsteady heat conduction problem. Its radial transient heat conduction analytical solution, i.e., the critical temperature propagation condition, is:

[0126] (1)

[0127] In the formula, T c —Minimum consolidation temperature of the coated sand, °C; T0—Original reservoir temperature, °C; T max—Maximum allowable temperature for coating sand, °C; erfc()—Complementary error function, which can be calculated by looking up a table in engineering; r e —Effective heating radius of the near-wellbore reservoir, m; α—Formation thermal diffusivity, m 2 / s;t p —Continuous injection time of heat pretreatment fluid, s.

[0128] The effective heating radius of the near-wellbore reservoir is based on the radial transient heat conduction theory, under conditions of continuous injection of isothermal pretreatment fluid and a continuous injection time t. p Under known conditions, the near-wellbore temperature influence range, i.e., the effective heating radius of the near-wellbore reservoir, can be expressed using a simplified engineering expression:

[0129] (2)

[0130] (3)

[0131] (4)

[0132] In the formula, ξ—complementary error coefficient, dimensionless; λ—formation thermal conductivity, W / (m·℃); ρ f —Effective density of the formation, kg / m³ 3 ;c f —Equivalent specific heat capacity of the formation, J / (kg·℃);

[0133] If the minimum liquid volume principle is satisfied, then r e =r w According to equation (4), the continuous injection time t of the heat pretreatment liquid can be calculated. p :

[0134] (5)

[0135] In the formula, r w —Wellbore radius, m;

[0136] b. Based on the effective heating radius of the near-wellbore reservoir, calculate the heat Q required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand. r ;

[0137] Simplifying the near-wellbore region into a homogeneous isotropic cylindrical formation unit, neglecting the axial temperature gradient and considering only radial heat conduction, the near-wellbore region temperature increases from the original reservoir temperature T0 to the minimum consolidation temperature T of the coated sand. c The total calories required are:

[0138] (6)

[0139] In the formula, Q r—The amount of heat required for the near-well reservoir to reach the minimum consolidation temperature of the coated sand, in J; L—Effective length of the well section, in m; —Reservoir porosity, %

[0140] c. The amount of heat Q required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand. r and the continuous injection time t of the heat pretreatment liquid p Calculate the inlet temperature T of the heat pretreatment liquid. p , heat pretreatment liquid pump injection and discharge rate q p ;

[0141] Calculate the heating heat after heat loss correction:

[0142] Considering the heat transfer due to the temperature difference between the wellbore and the formation, as well as the heat dissipation during the circulation process, and introducing a comprehensive thermal efficiency coefficient, the heating heat after heat loss correction is as follows:

[0143] (7)

[0144] In the formula, Q is the heating heat after heat loss correction, in J; η is the overall thermal efficiency coefficient, dimensionless, with a recommended value of 0.6-0.8.

[0145] Calculate the injection volume of the heat pretreatment fluid:

[0146] The effective heat that a unit volume of pretreatment liquid can provide is:

[0147] (8)

[0148] In the formula, Q p —Effective heat per unit volume of pretreated liquid, J / m³ 3 ;ρ p —Density of the heat pretreatment solution, kg / m³ 3 ;c p —Specific heat capacity of the heat pretreatment liquid, J / (kg·℃); T p —Inlet temperature of the heat pretreatment liquid, °C.

[0149] The minimum injection volume required for the heat pretreatment fluid is:

[0150] (9)

[0151] In the formula, V p —Minimum injection volume of heat pretreatment fluid, m 3 ;q p —Preheating pretreatment liquid pump injection / discharge rate, m 3 / s.

[0152] Calculate the injection and discharge rate q of the heat pretreatment liquid pump. p :

[0153] If the inlet temperature T of the heat pretreatment liquid is known p The combined equations (1)-(4) and (6)-(9) can be used to calculate the injection and discharge rate q of the heat pretreatment liquid pump. p :

[0154] (10)

[0155] Calculate the inlet temperature T of the heat pretreatment liquid. p :

[0156] If the injection / discharge rate q of the heat pretreatment liquid pump is known... p The inlet temperature T of the heat pretreatment liquid can be calculated by combining equations (1)-(4) and (6)-(9). p :

[0157] (11)

[0158] Specifically, the optimization of on-site construction parameters based on design parameters is carried out according to the following optimization principles:

[0159] Based on the above temperature-time-liquid volume coupling relationship, the following optimization criteria should be followed in the engineering implementation of this heat pretreatment liquid temperature and liquid volume design method:

[0160] a. Temperature Priority Principle: The inlet temperature of the heat pretreatment fluid should be maintained according to the following inequality to compensate for heat transfer losses in the wellbore:

[0161] (12)

[0162] b. Minimum Liquid Volume Principle: Select the minimum injection volume of the heat pretreatment liquid while meeting the following principles:

[0163] (13)

[0164] c. Construction time constraint principle: By increasing the injection and discharge rate q of the heat pretreatment liquid pump. p Or the inlet temperature T of the heat pretreatment liquid p This ensures that the pretreatment time is kept within the acceptable operating window of the deep-water platform, depending on the specific on-site operating conditions.

[0165] The advantages and features of the above-mentioned design method for the temperature and volume of the pre-treatment fluid and the near-wellbore reservoir before circulating filling are as follows: Through this temperature-time-volume coupling design method, the inlet temperature T of the pre-treatment fluid can be determined on-site. p The injection / discharge rate q of the heat pretreatment liquid pump can be calculated. p Or, given the injection / discharge rate q of the heat pretreatment liquid pump. p Calculate the inlet temperature T of the heat pretreatment liquid. pMeanwhile, the optimization principle of construction parameters can stably raise the near-wellbore reservoir temperature to the range where the coated sand can be consolidated, minimize the injected fluid volume and heat energy consumption, and calculate the continuous injection time t of the thermal pretreatment fluid through the minimum fluid volume principle. p This provides a reliable thermodynamic basis for the design method of subsequent hot liquid coating gravel filling and displacement liquid volume.

[0166] S3. Design method for hydrothermal coating, gravel filling, and displacement fluid volume of cryogenic reservoirs in ultra-deep water and ultra-shallow gas layers:

[0167] After completing the near-wellbore reservoir thermal pretreatment described in step S2, the near-wellbore temperature is brought to the minimum consolidation temperature T of the coated sand. c Subsequently, to ensure that the near-wellbore temperature remains within the solidification temperature range of the coated sand during the hot-carrying sand circulation filling process and for a duration of t... s For internal consolidation to be complete, the minimum inlet temperature T of the heat-carrying slurry must be controlled. s With the minimum displacement q of the cyclic filling s Collaborative design was carried out, and the duration t of thermally carried sand filling was also designed. s and displacement volume V s The core of this step is to establish a quantitative analytical relationship between the minimum inlet temperature of the thermally carried sand slurry, the duration of circulating filling, and the minimum discharge rate of circulating filling, so as to achieve the minimum inlet temperature T of the thermally carried sand slurry. s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The collaborative design ensures that the hot-carrying sand slurry circulation filling process meets the hot-carrying sand slurry filling duration t. s While meeting the requirements, it is necessary to minimize ineffective heat consumption and excessive injection of treatment fluid, and avoid excessive thermal disturbance and pollution to the reservoir. This will allow for optimized control of construction costs and energy consumption while ensuring sand control and wellbore support effectiveness, as detailed below:

[0168] S31. Establish a quantitative analytical relationship between the minimum inlet temperature of the thermally carried sand slurry, the duration of circulating filling, and the minimum displacement of circulating filling, in order to achieve the minimum inlet temperature T of the thermally carried sand slurry. s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The coordinated design ensures that the near-wellbore temperature remains at or above the minimum consolidation temperature of the coated sand during the hot-carrying sand circulation filling process, and remains above the minimum consolidation temperature of the coated sand for a duration of t. s Internal consolidation is completed;

[0169] Specifically, in step S31, the minimum inlet temperature of the thermally carried sand fluid is calculated based on the transient radial heat conduction analytical solution. Based on the lowest inlet temperature of the thermally carried sand slurry Given the total heat constraint of the heat-carrying sand liquid, the minimum displacement q for cyclic filling is obtained. s To achieve the lowest inlet temperature T of the thermally carried sand slurry s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s Collaborative design.

[0170] First, calculate the inlet temperature of the heat-carrying sand fluid circulation filling:

[0171] During the hot-carrying sand fluid circulation filling process, the temperature at the wellbore must always meet the following constraints:

[0172] (14)

[0173] in, This refers to the temperature at the wellbore wall at time t;

[0174] Based on the analytical solution of transient radial heat conduction, the temperature distribution of the reservoir at radius r at time t can be obtained:

[0175] (15)

[0176] In the formula, —Temperature of the reservoir at radius r at time t, where r is the radius extending from the wellbore axis towards the formation; T is the inlet temperature of the heat-carrying sand fluid circulation filling, in °C; t s —Duration of cyclic filling, s.

[0177] At the well wall, r=r w The lowest inlet temperature T of the heat-carrying sand fluid was obtained. s :

[0178] (16)

[0179] Secondly, calculate the minimum displacement for cyclic filling:

[0180] To ensure that during the cyclic filling duration t s Within the wellbore, the near-wellbore formation must always maintain a temperature no lower than the minimum consolidation temperature of the coated sand. The total heat provided by the heat-carrying sand fluid must meet the energy requirements for formation heating. The constraints are as follows:

[0181] (17)

[0182] Based on formulas (16) and (17), the minimum displacement for cyclic filling can be obtained:

[0183] (18)

[0184] In the formula, q s —Minimum displacement for cyclic filling, m3 / s;r c —Design consolidation control radius, m; ρ s —Density of thermally saturated sand, kg / m³ 3 ;c s —Specific heat capacity of heat-carrying sand liquid, J / (kg·℃);

[0185] According to equations (16) and (18), a given T can be achieved. s t s q s The system calculates any one of the three parameters to determine the other two, enabling coordinated design of the inlet temperature, filling time, and filling discharge rate of the thermally carried sand solution.

[0186] Calculate the volume of liquid used for thermally carried sand circulation filling:

[0187] (19)

[0188] In the formula, V s —The volume of liquid filled by the heat-carrying sand circulation system, in m 3 .

[0189] S32. Calculate the displacement liquid volume to achieve full replacement of the residual heat-carrying sand liquid in the annulus of the screen sleeve and inside the screen tube;

[0190] To ensure complete displacement of the filling section, the displacement liquid volume is calculated as follows:

[0191] (20)

[0192] In the formula, V d —Displacement fluid volume, m 3 β—Construction safety margin coefficient, recommended value is 0.2.

[0193] The temperature of the displacement solution is taken as the lowest solidification temperature of the coating sand, in °C.

[0194] The characteristics and advantages of the above-mentioned gravel filling and displacement liquid volume design method are as follows: taking the coating sand as the core control objective to be able to remain in the consolidation temperature range during the cyclic filling process and complete consolidation within a specified time, a quantitative analytical relationship is established between the injection temperature, duration, pump discharge rate and displacement liquid volume of the heat-carrying sand liquid. This avoids problems such as insufficient temperature, excessive injection or consolidation failure caused by traditional reliance on experience-based parameter selection, improves the stability of the filling structure and the long-term sand control reliability, and takes into account the construction efficiency and economy under ultra-deep water operation conditions, and has clear engineering feasibility.

[0195] Figure 4 A schematic diagram of the axial temperature control of the horizontal wellbore for optimized construction methods of sand-filling and sand-control completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs, with the wellbore radius r as the reference. wCentered on the ground, outwards are the coated sand consolidation zone, the effectively heated zone, and the original strata zone. The radius is less than r. c The area is the solidified zone of the coated sand, where the temperature T ≥ T c The consolidation condition is satisfied; when r c ≤R≤r e Even in the effective heating zone, the temperature is still higher than the minimum consolidation temperature T of the coated sand. c When r > r e The initial formation area was unaffected by heat, and the temperature remained at the original formation temperature T0. This figure reflects the radial temperature distribution characteristics of the near-wellbore region after hydrothermal injection, showing a decrease from high temperature outwards. Figure 5 This diagram illustrates the optimized construction method for sand control and well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs, specifically the temperature control during gravel packing operations. The horizontal axis represents time, and the vertical axis represents temperature, with T0 and T1 marked. c T s T p and T max Characteristic temperatures, etc. The construction process includes, in sequence, pre-construction, and reservoir pretreatment (lasting t). p ), Thermally carried sand molten material circulation filling stage (duration t) s ) and the displacement fluid replacement stage (lasting t) d The near-wellbore temperature gradually increases with the injection of the thermal pretreatment fluid and approaches or reaches the minimum consolidation temperature T. c During the hot-carrying sand circulation backfilling, the temperature was basically maintained at no less than T. c The temperature remains stable within the reservoir's range, fluctuating slightly during the replacement phase but generally remaining above the minimum consolidation temperature. After construction, the temperature gradually drops back to the original reservoir temperature. This figure reflects the process characteristics of achieving continuous consolidation conditions for the coated sand in the near-wellbore area through staged temperature control.

[0196] Example 2

[0197] This embodiment employs the methods described in S1, S2, and S3 above to optimize the sand control and well completion design of a horizontal well P in an ultra-deepwater, ultra-shallow gas reservoir in China. Specifically, a heated pretreatment fluid / heat-carrying sand fluid / sand-free displacement fluid is injected into the annulus pump using insulated tubing. First, the basic parameters of well P and the reservoir are prepared, as shown in Table 1.

[0198] Table 1. Basic parameters and data of P well and reservoir

[0199]

[0200] Based on the basic data for well P in the table above, use step S2 to calculate the injection / discharge rate q of the thermal pretreatment fluid pump. p Continuous injection time of heat pretreatment liquid t p The calculation results are shown in Table 2.

[0201] Table 2 Calculation results of parameters for the heat pretreatment stage of well P

[0202]

[0203] Based on the P-well baseline data, the cycle filling duration t was calculated using S3. s Minimum displacement q for cyclic filling s With displacement fluid volume V d The calculation results are shown in Table 3.

[0204] Table 3 Calculation results of parameters for the thermal sand circulation and displacement stages of Well P

[0205]

[0206] In summary, the optimized design parameters for sand control and sand-covered well completion of Well P are as follows:

[0207] Heat pretreatment stage: Inlet temperature of heat pretreatment liquid 80℃; Pump injection / discharge rate of heat pretreatment liquid 1.35m³. 3 / h; continuous injection time of heat pretreatment fluid: 3.36h; minimum required injection volume of heat pretreatment fluid: 4.54m³ 3 .

[0208] Thermally carried sand circulation filling stage: minimum inlet temperature of thermally carried sand slurry 70℃; minimum discharge rate of thermally carried sand slurry circulation filling 1.66m³. 3 / h; duration of thermally carried sand filling: 4.03h; volume of thermally carried sand circulating filling liquid: 6.68m³. 3 .

[0209] Displacement stage: Displacement liquid volume 306m³ 3 The temperature of the displacement solution is 20℃.

[0210] Based on the above-mentioned optimized design parameters for sand-coated sand control completion, the sand-coated filling sand control completion process, which was originally unable to be applied in ultra-deepwater and ultra-shallow gas cryogenic reservoirs due to the inability to achieve consolidation conditions, is now applied to ultra-deepwater and ultra-shallow gas cryogenic reservoirs, thereby achieving optimized design of the sand-coated sand control completion construction process for P-level wells.

Claims

1. An optimized construction method for sand-filling and sand-control completion of ultra-deepwater and ultra-shallow gas cryogenic reservoirs, characterized in that: Specifically, it includes: Step S1: A screen-tube coated sand circulation backfilling construction method for ultra-deep water and ultra-shallow gas cryogenic reservoirs that ensures the consolidation of coated sand. Heat pretreatment fluid is pumped into the annulus of the screen sleeve in the circulation channel to raise the original temperature of the reservoir near the well to the temperature range where the coated sand can solidify; then heat-carrying sand fluid is pumped into the annulus of the screen sleeve for circulation filling; after filling, sand-free displacement fluid is pumped into the annulus of the screen sleeve to fully replace the residual heat-carrying sand fluid in the annulus of the screen sleeve and the screen tube; after replacement, the circulation channel is closed and the construction is completed. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs also includes: Step S2: A method for designing the temperature and liquid volume of the near-wellbore reservoir during the pre-heat treatment stage of ultra-deepwater and ultra-shallow gas cryogenic reservoirs. This method designs the parameters of the pre-heat treatment fluid based on the characteristics of cryogenic consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation. Based on the designed parameters, the on-site construction parameters are optimized. The parameters of the pre-heat treatment fluid include the inlet temperature T. p , heat pretreatment liquid pump injection and discharge rate q p With the continuous injection time t of the heat pretreatment liquid p ; The parameter design of the thermal pretreatment fluid based on the low-temperature consolidation kinetics and the radial transient heat conduction law of the near-wellbore formation is as follows: Step A: Determine the effective heating radius r of the near-wellbore reservoir based on the critical temperature propagation condition. e Or the continuous injection time of the heat pretreatment liquid t p ; Step B: Based on the effective heating radius of the near-wellbore reservoir, calculate the heat Q required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand. r ; Step C: The amount of heat Q required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand. r and the continuous injection time t of the heat pretreatment liquid p Calculate the inlet temperature T of the heat pretreatment liquid. p , heat pretreatment liquid pump injection and discharge rate q p ; The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs also includes: Step S3: Design method for hydrothermal coating, gravel filling, and displacement fluid volume in ultra-deepwater and ultra-shallow gas cryogenic reservoirs: Step S31: Establish a quantitative analytical relationship between the minimum inlet temperature of the thermally carried sand slurry, the duration of circulating filling, and the minimum discharge rate of circulating filling, so as to achieve the minimum inlet temperature T of the thermally carried sand slurry. s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The coordinated design ensures that the near-wellbore temperature remains at or above the minimum consolidation temperature of the coated sand during the hot-carrying sand circulation filling process, and remains above the minimum consolidation temperature of the coated sand for a duration of t. s Internal consolidation is completed; Step S32: Calculate the displacement liquid volume to achieve full replacement of the residual heat-carrying sand liquid in the annulus of the screen sleeve and the screen tube.

2. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to claim 1, characterized in that, In step S1, the original temperature of the reservoir in the near-well area is raised to the minimum consolidation temperature of the coated sand.

3. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to claim 2, characterized in that, Step S1 specifically includes: Step a, Heat treatment of reservoir stage: After the completion string is run into the target well section and the structure is sealed, the heat pretreatment fluid is pumped into the screen pipe through the heat-insulated tubing or a special circulation string, and enters the screen sleeve annulus through the screen holes of the screen pipe to raise the original temperature of the reservoir in the near-well area to the minimum consolidation temperature of the coated sand. Step b, Thermally Carrying Sand Fluid Circulation and Filling Stage: After the heat treatment of the reservoir stage is completed, thermally carrying sand fluid containing coated sand is pumped into the screen pipe through the insulated oil pipe or a dedicated circulation string. The thermally carrying sand fluid carries the coated sand to the screen sleeve annulus and gradually deposits, accumulates and fills the screen sleeve annulus and near-wellbore voids under the action of circulation flow, forming a continuous and uniform particle accumulation layer. Step c, Replacement stage: After the heat-carrying sand fluid circulation and filling stage is completed, sand-free replacement fluid is pumped into the screen tube through the heat-insulated oil pipe or a special circulation pipe string to fully replace the residual heat-carrying sand fluid inside the screen tube and the screen sleeve annulus. After step d, the replacement phase, is completed, the circulation channel is closed and the construction is finished.

4. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to claim 1, characterized in that, In step A, when the minimum liquid volume principle is met, i.e., the effective heating radius of the near-wellbore reservoir is equal to the wellbore radius and is a known quantity, the continuous injection time t of the thermal pretreatment fluid is calculated using the effective heating radius of the near-wellbore reservoir. p When the heat pretreatment liquid is continuously injected for time t p When the quantity is known, the effective heating radius of the near-wellbore reservoir can be calculated, as follows: The critical temperature propagation condition is as follows: (1) In the formula, T c —Minimum consolidation temperature of the coated sand, °C; T0—Original reservoir temperature, °C; T max —Maximum allowable temperature for coating sand, °C; erfc()—Complementary error function, calculated in engineering by looking up a table; r e —Effective heating radius of the near-wellbore reservoir, m; α—Formation thermal diffusivity, m 2 / s;t p —Continuous injection time of heat pretreatment fluid, s; The effective heating radius of the near-wellbore reservoir, based on the radial transient heat conduction theory, is determined under conditions of continuous injection of a constant-temperature pretreatment fluid for a duration of t. p Under known conditions, the near-wellbore temperature influence range, i.e., the effective heating radius of the near-wellbore reservoir, is expressed using a simplified engineering expression: (2) (3) (4) In the formula, ξ is the complementary error coefficient, which is dimensionless. λ—formation thermal conductivity, W / (m·℃); ρ f —Effective density of the formation, kg / m³ 3 c f —Equivalent specific heat capacity of the formation, J / (kg·℃); If the minimum liquid volume principle is satisfied, then r e =r w The continuous injection time t of the heat pretreatment liquid is calculated according to equation (4). p : (5) In the formula, r w — Wellhead radius, m; The amount of heat required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand, as described in step B: Simplifying the near-wellbore region into a homogeneous isotropic cylindrical formation unit, neglecting the axial temperature gradient and considering only radial heat conduction, the near-wellbore region temperature increases from the original reservoir temperature T0 to the minimum consolidation temperature T of the coated sand. c The total calories required are: (6) In the formula, Q r —The amount of heat required for the near-wellbore reservoir to reach the minimum consolidation temperature of the coated sand, in J; L—Effective length of the well section, in m; —Reservoir porosity, % Step C includes: Calculate the heating heat after heat loss correction: Considering the heat transfer due to the temperature difference between the wellbore and the formation, as well as the heat dissipation during the circulation process, and introducing a comprehensive thermal efficiency coefficient, the heating heat after heat loss correction is: (7) In the formula, Q is the heating heat after heat loss correction, in J; η is the overall thermal efficiency coefficient, dimensionless, with a recommended value of 0.6-0.8; Calculate the injection volume of the heat pretreatment fluid: The effective heat that a unit volume of pretreatment liquid can provide is: (8) In the formula, Q p —Effective heat per unit volume of pretreated liquid, J / m³ 3 ;ρ p —Density of the heat pretreatment solution, kg / m³ 3 c p —Specific heat capacity of the heat pretreatment liquid, J / (kg·℃); T p —Inlet temperature of the heat pretreatment liquid, °C; The minimum injection volume required for the heat pretreatment fluid is: (9) In the formula, V p —Minimum injection volume of heat pretreatment fluid, m 3 ;q p —Preheating pretreatment liquid pump injection / discharge rate, m 3 / s; If the inlet temperature T of the heat pretreatment liquid is known p The injection and discharge rate q of the heat pretreatment liquid pump is calculated according to formula (10). p : (10) If the injection / discharge rate q of the heat pretreatment liquid pump is known... p The inlet temperature T of the heat pretreatment liquid is calculated according to formula (11). p : (11)。 5. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to claim 1, characterized in that, The optimization of on-site construction parameters based on design parameters shall be carried out according to the following priority principles: Principle a. Temperature Priority Principle: The inlet temperature of the thermal pretreatment fluid should be guaranteed to meet the following inequality to compensate for heat transfer losses in the wellbore: (12) Principle b. Minimum Liquid Volume Principle: Select the minimum injection volume of the heat pretreatment liquid while meeting the following principles: (13) Principle c. Construction time constraint principle: By increasing the injection and discharge rate q of the heat pretreatment liquid pump. p Or the inlet temperature T of the heat pretreatment liquid p The heat pretreatment liquid is continuously injected for a time t. p Keep operations within the acceptable operating window for deep-water platforms.

6. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to claim 1, characterized in that, In step S31, the minimum inlet temperature T of the heat-carrying sand fluid is calculated based on the transient radial heat conduction analytical solution. s Based on the lowest inlet temperature T of the thermally carried sand slurry s Given the total heat constraint of the heat-carrying sand liquid, the minimum displacement q for cyclic filling is obtained. s To achieve the lowest inlet temperature T of the thermally carried sand slurry s , Cyclic filling duration t s and the minimum displacement q of the cyclic filling s The collaborative design, and based on the cycle filling duration t s and the minimum displacement q of the cyclic filling s Calculate the volume of liquid used for thermally carried sand circulation filling.

7. The optimized construction method for sand-filling and sand-controlling well completion in ultra-deepwater and ultra-shallow gas cryogenic reservoirs according to claim 6, characterized in that, Step S31 specifically involves: First, calculate the inlet temperature of the heat-carrying sand fluid circulation filling: During the hot-carrying sand fluid circulation filling process, the temperature at the wellbore must always meet the following constraints: (14) in, This refers to the temperature at the wellbore wall at time t; Based on the analytical solution of transient radial heat conduction, the temperature distribution of the reservoir at radius r at time t can be obtained: (15) In the formula, —Temperature of the reservoir at radius r at time t, where r is the radius extending from the wellbore axis towards the formation; T is the inlet temperature of the heat-carrying sand fluid circulation filling, in °C; t s —Duration of the cycle filling, in seconds; At the well wall, r=r w The lowest inlet temperature of the heat-carrying sand fluid was obtained. : (16) Secondly, calculate the minimum displacement for cyclic filling: To ensure that during the cyclic filling duration t s Within the wellbore region, the temperature must be maintained at or above the minimum consolidation temperature of the coated sand. The total heat provided by the heat-carrying sand fluid must meet the energy requirements for formation heating. The constraints are as follows: (17) Based on formulas (16) and (17), the minimum displacement for cyclic filling can be obtained: (18) In the formula, q s —Minimum displacement for cyclic filling, m 3 / s;r c —Design consolidation control radius, m; ρ s —Density of thermally saturated sand, kg / m³ 3 c s —Specific heat capacity of heat-carrying sand liquid, J / (kg·℃); Calculate the volume of liquid used for thermally carried sand circulation filling: (19) In the formula, V s —The volume of liquid filled by the heat-carrying sand circulation system, in m 3 ; The displacement fluid volume mentioned in step S32 is calculated according to the following formula: (20) In the formula, V d —Displacement fluid volume, m 3 ; β—Construction safety margin coefficient, dimensionless.

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