Method for improving steam huff-puff development effect of superficial super heavy oil reservoir

Abstract

The invention provides a method for improving the steam huff and puff development effect of a shallow super heavy oil reservoir, and the method comprises the steps: S1, optimizing the steam injection amount of a first slug, and injecting a first steam slug into the oil reservoir; s2, according to the well bottom temperature measurement curve, the position of a high flow guide channel is judged, and the demand quantity of a temporary plugging agent is calculated; s3, the type of a temporary plugging agent is optimized, and the temporary plugging agent is directionally injected into the oil reservoir; s4, the steam injection amount of the second slug is optimized, and a second steam slug is injected into the oil reservoir; s5, soaking the well, and turning to production after the temperature field is expanded and the temporary plugging agent loses efficacy; and S6, carrying out cycle production by taking daily oil production as a cut-off condition. The recovery efficiency of the superficial extra-super heavy oil reservoir is effectively improved, and the method for improving the development effect of the superficial extra-super heavy oil reservoir through directional temporary plugging is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and particularly relates to a method for improving the steam huff and puff development effect of a shallow extra - heavy oil reservoir. Background Art

[0002] The shallow extra - heavy oil reservoir in the western part of Shengli has a shallow burial depth, 200 - 500 meters, a relatively low reservoir pressure, 1.2 - 4.8 MPa, and a high crude oil viscosity, 400 - 1000×10 4 mPa·s at formation temperature. This type of heavy oil reservoir has no stable rock skeleton and belongs to the "sand - in - oil" type. During the steam injection process, the steam injection pressure is generally more than twice the reservoir pressure, which will form high - conductivity channels; during the production process, affected by factors such as crude oil viscosity and pressure field changes, the high - conductivity channels close, and the steam entering the deep part of the reservoir cannot flow back to the bottom hole, the pressure in the near - wellbore area drops rapidly, the production time of the huff and puff wells is short, and the development effect is poor, as Figure 2 shown. This also causes that during the steam huff and puff process of shallow extra - heavy oil, too little steam is injected, the heat energy provided is insufficient, and the viscosity reduction effect is not ideal; too much steam is injected, the channeling is serious, the water recovery rate is low, and the thermal efficiency is low. There is an optimal steam injection volume for each high - conductivity channel, which can improve the thermal efficiency while ensuring the heating effect. Therefore, increasing the number of high - conductivity channels is the key to improving the steam huff and puff development effect of shallow extra - heavy oil.

[0003] Using temporary plugging agents can increase the number of high - conductivity channels and improve the steam huff and puff development effect of shallow extra - heavy oil reservoirs. By calculating the thermal efficiency under different steam injection volumes, the pre - steam slug volume is optimized; after pre - injecting steam, through the bottom - hole temperature measurement curve, the heat - concentrated area is found, the position of the high - conductivity channel is judged, the temperature distribution of the high - conductivity channel is normalized, and the temporary plugging agent demand for high - conductivity channels at different positions is calculated; according to the crude oil viscosity and the scale of the high - conductivity channel, the type of temporary plugging agent (inorganic temporary plugging agent, organic temporary plugging agent, inorganic temporary plugging agent + organic temporary plugging agent) is selected, and the high - strength temporary plugging agent is directionally injected by using a packer. The temporary plugging agent preferentially enters the high - conductivity channel, increasing the seepage resistance of this channel, plugging the high - conductivity channels in sequence, then using numerical simulation methods to optimize the subsequent steam injection volume, injecting another slug of steam, and the subsequent injected steam will promote the emergence of new channels, realizing the transformation from long and narrow channels to short and wide channels. After the steam injection is completed, soak the well, wait for the steam to transfer heat and mass with the reservoir and the temporary plugging agent to fail, and then switch to production. After the production is completed, switch to the next cycle of huff and puff development.

[0004] In the conventional plugging process, plugging agents generally act on the steam channel between multiple wells. The longer the plugging time of the high conductivity channel, the better, at least one cycle. The blocked channel contributes less to the production capacity. The flow law of shallow ultra-heavy oil reservoirs is special. The oil saturation inside the high conductivity channel is high, and the development potential is large. It is not suitable for long-term plugging. Figure 3 The temporary plugging agent only temporarily blocks the high conductivity channel. After a period of time, the temporary plugging agent becomes ineffective and the blocked channel can continue to supply fluid to the well. Figure 4 As shown. At the same time, the slug-type steam injection is conducive to the mass and heat transfer between the front steam slug and the reservoir, improves the steam heat utilization rate, reduces the crude oil viscosity more evenly, and reduces the fingering phenomenon of the subsequent steam slug; the one-time steam injection will form a small number of long and narrow high-conductivity channels. The injection of temporary plugging agent can temporarily plug the channel formed by the front steam slug, and the subsequent steam slug will form a new high-conductivity channel, thereby increasing the number of channels and promoting steam to concentrate on heating the crude oil near the huff-and-puff well, forming a wide and short high-conductivity channel, thereby improving the steam huff-and-puff development effect of shallow ultra-heavy oil.

[0005] The patent "A step design method for multi-directional viscosity reduction after multiple rounds of heavy oil huff and puff" proposes a method to use the temperature change curve of the oil layer in the radial direction of the huff and puff well to achieve fine division of the oil layer, so as to accurately use the remaining oil, improve the thermal utilization rate of steam, and improve the steam huff and puff development effect. This method is aimed at the problem that the residual oil saturation in the near-well area is low during the multiple rounds of huff and puff stage, and the oil leakage radius is difficult to further expand effectively. It does not consider the problem of uneven initial production of shallow ultra-heavy oil. At the same time, the steam is injected into the reservoir at one time, and there are also differences in the injection mode. The patent "Method for late-stage production of thin-layer heavy oil reservoirs after multiple rounds of huff and puff" proposes to improve the late-stage development effect of thin-layer heavy oil reservoirs after multiple rounds of huff and puff using nitrogen and microemulsion-assisted steam. This method is aimed at the contradiction that the production of thin-layer heavy oil in the late stage of multiple rounds of huff and puff is fast, the water content is fast, and the energy decreases, resulting in poor production effect. The purpose is to increase the formation energy, improve the steam sweep and oil washing efficiency. The steam is injected once, and the particularity of the steam injection law of shallow ultra-heavy oil is not considered. The patent "A method for plugging and regulating oil reservoirs" proposes a method for determining the types of water drive zones at different locations based on the residual oil saturation, and based on the types of water drive zones, calling the corresponding plugging and regulating model to determine the corresponding plugging and regulating system and system dosage. This method is aimed at conventional water drive oil reservoirs, and there are differences in development rules and selection of plugging agent types compared with heavy oil steam stimulation.

[0006] There is currently no precedent at home and abroad for using directional temporary plugging agents to improve the development of shallow ultra-heavy oil reservoirs, and there is a lack of theoretical and practical guidance. Summary of the invention

[0007] In view of the above problems, the present invention is proposed to provide a method for improving the steam stimulation development effect of a shallow extra - heavy oil reservoir, which can overcome the above problems or at least partially solve the above problems.

[0008] According to one aspect of the present invention, there is provided a method for improving the steam stimulation development effect of a shallow extra - heavy oil reservoir, the improvement method comprising:

[0009] Step S1, optimizing the steam injection volume of slug one and injecting the first steam slug into the reservoir;

[0010] Step S2, judging the position of the high - conductivity channel according to the bottom - hole temperature measurement curve and calculating the demand for the temporary plugging agent;

[0011] Step S3, preferably selecting the type of the temporary plugging agent and injecting the temporary plugging agent into the reservoir directionally;

[0012] Step S4, optimizing the steam injection volume of slug two and injecting the second steam slug into the reservoir;

[0013] Step S5, soaking the well, and after waiting for the temperature field to expand and the temporary plugging agent to fail, switching to production;

[0014] Step S6, taking the daily oil production as the cut - off condition and carrying out cyclic production.

[0015] Optionally, the step S1, optimizing the steam injection volume of slug one and injecting the first steam slug into the reservoir specifically includes:

[0016] Collecting the reservoir physical properties of the target block, establishing a numerical simulation model, and optimizing the injection volume of the first steam slug with the thermal efficiency as the evaluation criterion.

[0017] Optionally, the calculation method of the thermal efficiency is:

[0018]

[0019] Wherein, x, y, and z are the grid numbers in the horizontal, vertical, and longitudinal directions of the numerical model, is the porosity of the grid at any position, S wijk 、S oijk 、S gijk are the water saturation, oil saturation, and gas saturation at any position, c w 、c o 、c g 、c r are the specific heat capacities of water, oil, gas, and rock skeleton, V ijk is the grid volume at any position, T ijk is the grid temperature at any position, T 0 is the original temperature of the reservoir, T s is the steam temperature, a is the steam dryness, Lv is the latent heat of steam, V w is the equivalent volume of the injected steam water.

[0020] Optionally, in step S2, judging the position of the high-permeability channel and calculating the demand for the temporary plugging agent according to the bottom-hole temperature measurement curve specifically includes:

[0021] Judging the position of the high-permeability channel according to the bottom-hole temperature curve after the steam injection in step S1, and calculating the demand for the temporary plugging agent at different positions.

[0022] Optionally, judging the position of the high-permeability channel specifically includes:

[0023] There is a temperature inflection point between the peak and valley of the temperature curve. Take several points near the curve inflection point and draw the curve segment M n N n , and the corresponding abscissa is denoted as [i n , i n ’], and perform regression fitting on the line segment. The regression function is as follows:

[0024] f n (i) = ax 3 + bx 2 + cx + d (2)

[0025] where a, b, c, and d are dimensionless coefficients obtained through relevant data fitting software;

[0026] Obtain the curvature K 1 N 1 of the curve segment M n , i n ’], and the calculation formula is as follows: n

[0027]

[0028] Obtain the abscissa i 1 corresponding to the maximum curvature value on the curve segment MN 1 nmax ;

[0029] The obtaining method is solved by the first derivative method of the function or the mathematical optimization algorithm;

[0030] If n abscissas are obtained on the temperature curve, there are n + 1 segments during the steam injection process. Among them, the area with the temperature peak has a high-permeability channel, and the number is m, and m is equal to n / 2 or (n + 1) / 2.

[0031] Optionally, calculating the demand for the temporary plugging agent at different positions specifically includes:

[0032] Integrate the temperature curve segments where the high-permeability channels are located respectively;

[0033] Each temperature curve segment contains multiple temperature measurement points, which is equivalent to the differentiation of the temperature curve. Accumulate the data of the temperature measurement points to obtain the superimposed temperature of this segment. The calculation formula is as follows:

[0034]

[0035] Among them, T j is the temperature of the temperature measurement point, and T 0 is the original temperature of the reservoir.

[0036] Optionally, the integration of the temperature curve segments where the high-permeability channels are located respectively further includes:

[0037] Perform regression fitting on the curve segments where the high-permeability channels are located respectively, denoted as the function F m (i), and then use mathematical methods to perform definite integration on the regression formula to obtain the superimposed temperature of this segment. The calculation formula is as follows:

[0038]

[0039] According to the integration results, calculate the percentage ratio of each superimposed temperature. The calculation formula is as follows:

[0040]

[0041] Combined with the steam injection volume of slug 1, calculate the demand for the temporary plugging agent for each segment. The calculation formula is as follows:

[0042] V i =x i β max V w (7)

[0043] Among them, β max is the optimal temporary plugging coefficient, and V w is the steam injection volume of slug 1.

[0044] Optionally, the optimal temporary plugging coefficient is obtained through indoor physical simulation, specifically including:

[0045] Select the oil sample of the target reservoir to carry out a two-dimensional visualization experiment. After injecting a steam slug, inject different amounts of the temporary plugging agent respectively. The ratio of the amount of the temporary plugging agent to the volume of the first steam slug is the temporary plugging coefficient. Statistically analyze the enlarged proportion of the swept volume of the second steam slug in different experimental schemes, and select the optimal temporary plugging coefficient.

[0046] Optionally, the method for selecting the optimal temporary plugging coefficient is:

[0047] Collect the enlarged proportions of the steam swept volume under different temporary plugging coefficients, and the regression fitting formula is as follows:

[0048] f(β) = eln(β) + g(8)

[0049] where e and g are dimensionless coefficients obtained through relevant data fitting software;

[0050] Obtain the curvature K of the curve β , and the calculation formula is as follows:

[0051]

[0052] Obtain the abscissa β corresponding to the maximum curvature value on the curve max , which is the optimal temporary plugging coefficient;

[0053] The obtaining method is solved by using the first derivative method of the function or the mathematical optimization algorithm.

[0054] Optionally, in step S3, when optimizing the type of temporary plugging agent and directionally injecting the temporary plugging agent into the reservoir, it specifically includes:

[0055] According to the crude oil viscosity and the high-permeability channel scale calculated in step 2, optimize the type of temporary plugging agent. According to the demand of the plugging agent for the high-permeability channel calculated in step S2, use a packer to directionally inject the temporary plugging agent into the n - 1 section, and the injection sequence is from the bottom of the well to the wellhead direction.

[0056] Optionally, the screening method of the temporary plugging agent includes:

[0057] Establish a numerical model of shallow extra-heavy oil at a certain viscosity. By adjusting the reservoir heterogeneity, construct high-permeability channels of different scales, and inject inorganic temporary plugging agents, organic temporary plugging agents, and inorganic + organic temporary plugging agents respectively. Compare the plugging effects and input costs to obtain the best temporary plugging agent corresponding to the corresponding scale;

[0058] Change the crude oil viscosity and repeat the relevant calculations to obtain the best temporary plugging agents at different viscosities and different high-permeability channel scales.

[0059] Optionally, in step S4, when optimizing the steam injection volume of slug two and injecting the second steam slug into the reservoir, it specifically includes: Optimize and calculate the steam injection volume of slug two by using the numerical simulation method, and select the cyclic oil production as the evaluation criterion.

[0060] Optionally, in step S5, during the soaking period, after waiting for the temperature field to expand and the temporary plugging agent to fail, switching to production specifically includes:

[0061] Close the well for soaking, wait for the mass transfer and heat transfer between the steam and the reservoir, and the failure of the temporary plugging agent. The soaking time is 2 - 5 days, and then open the well for production.

[0062] Optionally, in step S6, taking the daily oil production as the cut-off condition, the cyclic production specifically includes: taking the daily oil production as the production cut-off condition, selecting 1 - 2 t / d, then injecting steam, and proceeding with the development of the next cycle.

[0063] An improvement method for the steam huff and puff development effect of a shallow extra - heavy oil reservoir provided by the present invention, the improvement method includes: step S1, optimizing the steam injection volume of slug 1 and injecting the first steam slug into the reservoir; step S2, judging the position of the high - conductivity channel according to the bottom - hole temperature measurement curve and calculating the demand for the temporary plugging agent; step S3, preferably selecting the type of the temporary plugging agent and directionally injecting the temporary plugging agent into the reservoir; step S4, optimizing the steam injection volume of slug 2 and injecting the second steam slug into the reservoir; step S5, soaking the well, waiting for the temperature field to expand and the temporary plugging agent to fail, and then switching to production; step S6, taking the daily oil production as the cut - off condition and proceeding with cyclic production. It can effectively improve the recovery factor of the shallow extra - heavy oil reservoir and form a method for improving the development effect of the shallow extra - heavy oil reservoir by directional temporary plugging.

[0064] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the description. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are given below. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0066] Figure 1 It is a flowchart of an improvement method for the steam huff and puff development effect of a shallow extra - heavy oil reservoir provided by an embodiment of the present invention;

[0067] Figure 2 It is a schematic diagram of the change of the high - conductivity channel during the steam huff and puff process of a shallow extra - heavy oil reservoir provided by an embodiment of the present invention;

[0068] Figure 3 It is a schematic diagram of a conventional plugging agent plugging the steam channeling channel of a conventional heavy oil reservoir provided by an embodiment of the present invention;

[0069] Figure 4 It is a schematic diagram of a temporary plugging agent plugging the high - conductivity channel of a shallow extra - heavy oil reservoir provided by an embodiment of the present invention;

[0070] Figure 5 It is a schematic diagram of the distribution of steam injected at one time and steam injected in a slug - type manner during the steam huff and puff of a shallow extra - heavy oil reservoir of the present invention;

[0071] Figure 6 This is the screening criteria for temporary plugging agents in an example of the present invention;

[0072] Figure 7 This is the optimized curve of the steam injection volume of slug 1 in Example 1;

[0073] Figure 8 This is the bottom-hole temperature curve at the end of steam injection for slug 1 in Example 1;

[0074] Figure 9 This is curve segment M in Example 1 n N n and the regression fitting function;

[0075] Figure 10 This is the regression fitting function of the temporary plugging coefficient in Example 1;

[0076] Figure 11 This is the optimized curve of the steam injection volume of slug 2 in Example 1;

[0077] Figure 12 This is the production degree curves of conventional steam huff and puff and directional temporary plugging steam huff and puff in Example 1. Detailed implementation manners

[0078] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0079] The terms "including" and "having" and any variations thereof in the description, embodiments and claims of the present invention are intended to cover non-exclusive inclusion. For example, including a series of steps or units.

[0080] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0081] Based on the reservoir physical properties of the target block, a numerical model is established, the injection volume of the first steam slug is optimized, the position of the high-permeability channel is judged according to the bottom-hole temperature curve at the end of steam injection, the demand for temporary plugging agents is calculated, the temporary plugging agents are injected directionally using a packer, the injection volume of the second steam slug is optimized using numerical simulation methods, the transformation from a long and narrow channel to a short and wide channel is realized, the soaking period is waited for the temperature to increase and the temporary plugging agents to fail, and then production development is carried out, finally expanding the oil drainage volume, improving the utilization degree of the near-well zone, and improving the steam huff and puff development effect of the shallow extra-heavy oil reservoir.

[0082] The features and performance of the present invention will be further described in detail below in conjunction with specific embodiments.

[0083] In the process of steam huff and puff development of shallow extra - heavy oil reservoirs, the present invention aims at the contradictory problems such as shallow burial depth of the reservoir, thin oil layers, high viscosity of crude oil, resulting in low formation temperature, high viscosity of crude oil underground and inability to flow normally, as well as fast heat dissipation during steam injection and easy steam fingering. It innovatively proposes the concept of using temporary plugging agents to achieve steam diversion and increase the number of high - conductivity channels during thermal recovery steam injection. Combining with the algorithm for calculating steam fingering, it can control the depth of steam fingering and channeling, ensure that the steam concentrates on heating the crude oil in the near - wellbore area, and improve the thermal utilization rate of the injected steam. At the same time, it innovatively establishes a method for judging high - conductivity channels, guiding the selection of the injection position of temporary plugging agents and the optimization of process technologies; a method for calculating the demand for temporary plugging agents is established to guide the optimization of the dosage of temporary plugging agents in actual production; and a screening and optimization standard for temporary plugging agents is established to guide the selection of temporary plugging types. The core idea is as Figure 4 , Figure 5 shown.

[0084] The specific methods involved in the present invention include: optimizing the pre - steam slug volume by calculating the thermal efficiency at different steam injection volumes; after pre - injecting steam, finding the heat - concentrated area through the bottom - hole temperature measurement curve, judging the position of high - conductivity channels, normalizing the temperature distribution of high - conductivity channels, and calculating the demand for temporary plugging agents at different positions of high - conductivity channels; selecting the type of temporary plugging agent (inorganic temporary plugging agent, organic temporary plugging agent, inorganic temporary plugging agent + organic temporary plugging agent) according to the crude oil viscosity and the scale of high - conductivity channels, and using a packer to achieve the directional injection of high - strength temporary plugging agents; using numerical simulation methods to optimize the injection volume of subsequent steam to achieve the transformation from long and narrow channels to short and wide channels, and after the steam injection is completed, soaking the well, waiting for the steam to transfer heat and mass with the reservoir and the temporary plugging agent to fail, and then switching to production.

[0085] As Figure 1 shown, the specific steps of the present invention include:

[0086] Step 1, optimize the steam injection volume of slug 1 and inject the first steam slug into the reservoir;

[0087] Step 2, judge the position of high - conductivity channels and calculate the demand for temporary plugging agents according to the bottom - hole temperature measurement curve;

[0088] Step 3, optimize the type of temporary plugging agent and inject the temporary plugging agent directionally into the reservoir;

[0089] Step 4, optimize the steam injection volume of slug 2 and inject the second steam slug into the reservoir;

[0090] Step 5, soak the well, and after waiting for the temperature field to expand and the temporary plugging agent to fail, switch to production;

[0091] Step 6: Carry out cyclic production with the daily oil production as the cut-off condition.

[0092] The object of the present invention can also be achieved by the following technical measures:

[0093] In Step 1, collect the reservoir physical properties of the target block, establish a numerical simulation model, and optimize the injection volume of the first steam slug with the thermal efficiency as the evaluation criterion.

[0094] The thermal efficiency calculation method is as follows:

[0095]

[0096] Among them, x, y, and z are the grid numbers in the horizontal, vertical, and longitudinal directions of the numerical model, is the grid porosity at any position, S wijk , S oijk , S gijk are the water saturation, oil saturation, and gas saturation at any position, c w , c o , c g , c r are the specific heat capacities of water, oil, gas, and rock skeleton, V ijk is the grid volume at any position, T ijk is the grid temperature at any position, T 0 is the original reservoir temperature, T s is the steam temperature, a is the steam quality, L v is the latent heat of steam, V w is the equivalent volume of injected steam water.

[0097] The parameters in the calculation method are all collected in the numerical model.

[0098] In Step 2, according to the bottom-hole temperature curve after the steam injection in Step 1, judge the position of the high-permeability channel and calculate the demand for temporary plugging agent at different positions.

[0099] As Figure 2 shown, schematic diagram of the change of high-permeability channel during steam stimulation in shallow extra-heavy oil reservoir. As Figure 3 shown, schematic diagram of the conventional plugging agent plugging the steam channeling channel in conventional heavy oil reservoir.

[0100] The position of the high-permeability channel can be judged by the following method.

[0101] There is a temperature inflection point between the peak and trough of the temperature curve. Take several points near the curve inflection point and draw the curve segment M n N n , and record the corresponding abscissa as [i n , i n '], and perform regression fitting on the line segment. The regression function is as follows:

[0102] f n (i) = ax 3 + bx 2 + cx + d (2)

[0103] Among them, a, b, c, and d are dimensionless coefficients, which can be obtained through relevant data fitting software.

[0104] Obtain the curve segment M 1 N 1 The curvature K n , i n ’] is calculated as follows: n The calculation formula is as follows:

[0105]

[0106] Obtain the curve segment M 1 N 1 The abscissa i corresponding to the maximum curvature value on nmax ; The solution method uses the first derivative method of the function or the mathematical optimization algorithm for solution;

[0107] Using the same method, n abscissas are obtained on the temperature curve. Then, there are n + 1 segments during the steam injection process. Among them, the region with the temperature peak has high-conductivity channels, and the number is m, where m is equal to n / 2 or (n + 1) / 2.

[0108] The calculation of the temporary plugging agent demand can be carried out through the following method.

[0109] Integrate the temperature curve segments where the high-conductivity channels are located respectively, and there are two methods.

[0110] Method 1: Each temperature curve segment contains multiple temperature measurement points, which is equivalent to the differentiation of the temperature curve. Accumulate the temperature measurement point data to obtain the superimposed temperature of this segment. The calculation formula is as follows:

[0111]

[0112] Among them, T j is the temperature at the temperature measurement point, and T 0 is the original temperature of the reservoir.

[0113] Method 2: Perform regression fitting on the curve segments where the high-conductivity channels are located respectively, denoted as the function F m (i), and then use mathematical methods to perform definite integration on the regression formula to obtain the superimposed temperature of this segment. The calculation formula is as follows:

[0114]

[0115] According to the integration result, calculate the occupancy ratio of the superimposed temperature for each section. The calculation formula is as follows:

[0116]

[0117] Combined with the steam injection volume of slug 1, calculate the demand for the temporary plugging agent for each section. The calculation formula is as follows:

[0118] V i = x i β max V w (7)

[0119] Where, β max is the optimal temporary plugging coefficient, and V w is the steam injection volume of slug 1.

[0120] The optimal temporary plugging coefficient β max can be obtained through indoor physical simulation:

[0121] Select the oil sample of the target reservoir to carry out a two-dimensional visualization experiment. After injecting a steam slug, inject different amounts of the temporary plugging agent respectively. The ratio of the amount of the temporary plugging agent to the volume of the first steam slug is the temporary plugging coefficient. Statistically analyze the enlarged ratio of the swept volume of the second steam slug in different experimental schemes, and select the optimal temporary plugging coefficient.

[0122] The method for selecting the optimal temporary plugging coefficient is to collect the enlarged ratio of the steam swept volume under different temporary plugging coefficients, and the regression fitting formula is as follows:

[0123] f(β) = eln(β)+g (8)

[0124] Where, e and g are dimensionless coefficients, which can be obtained through relevant data fitting software.

[0125] Obtain the curvature K β on the curve. The calculation formula is as follows:

[0126]

[0127] Obtain the abscissa β max corresponding to the maximum curvature value on the curve, which is the optimal temporary plugging coefficient; the obtaining method can adopt the first derivative method of the function or the mathematical optimization algorithm for solution.

[0128] In step 3, according to the crude oil viscosity and the high-permeability channel scale calculated in step 2, optimize the type of the temporary plugging agent. According to the demand for the plugging agent for the high-permeability channel calculated in step 2, use a packer to inject the temporary plugging agent into section n - 1 in a directional manner, and the injection sequence is from the bottom of the well to the wellhead direction.

[0129] The screening of the temporary plugging agent can be obtained by the following method.

[0130] A numerical model of shallow extra - heavy oil at a certain viscosity is established. By adjusting the reservoir heterogeneity, high - conductivity channels of different scales are constructed. Inorganic temporary plugging agents, organic temporary plugging agents, and inorganic + organic temporary plugging agents are injected respectively. The plugging effects and input costs are compared to obtain the best temporary plugging agent at this scale. By changing the crude oil viscosity and repeating the relevant calculations, the best temporary plugging agents at different viscosities and different high - conductivity channel scales are obtained, as Figure 6 shown. The preferred criteria for the temporary plugging agent are as follows:

[0131] For reservoirs with a high - conductivity channel scale less than 50 m and a crude oil viscosity less than 20000 mPa·s, choose an inorganic temporary plugging agent or an organic temporary plugging agent for temporary plugging; for reservoirs with a high - conductivity channel scale less than 50 m and a crude oil viscosity greater than 20000 mPa·s, choose an organic - type temporary plugging agent; for reservoirs with a high - conductivity channel scale greater than 50 m and a crude oil viscosity less than 20000 mPa·s, choose an inorganic temporary plugging agent for temporary plugging; for reservoirs with a high - conductivity channel scale greater than 50 m and a crude oil viscosity greater than 20000 mPa·s, choose an inorganic temporary plugging agent + organic - type temporary plugging agent, with a volume ratio of 5:5.

[0132] In step 4, the steam injection volume of slug two is optimized by numerical simulation method, and the evaluation criterion is the periodic oil production.

[0133] In step 5, shut in the well for soaking, waiting for the mass transfer and heat transfer between the steam and the reservoir, and the failure of the temporary plugging agent. Generally, the soaking time is 2 - 5 days, and then open the well for production.

[0134] In step 6, take the daily oil production as the production cut - off condition, generally choose 1 - 2 t / d,

[0135] Then inject steam to carry out the next - cycle development.

[0136] Example 1

[0137] Taking the shallow extra - heavy oil reservoir A as an example, the present invention conducts directional temporary plugging to improve steam stimulation development, including the following steps:

[0138] Step 1: The burial depth of reservoir A is 346 - 357 m, and the effective thickness is 3.5 m. The injection volume of the first steam slug is optimized by numerical simulation method to be 600 t, as Figure 7 shown;

[0139] Step 2: The horizontal well is 200 m long, and the temperature curve is as Figure 8 shown. Select the curve segment for regression to obtain Figure 9 , calculate the regression formula to obtain that the high - conductivity channels are distributed in the range of 0 - 46 m. Because there is only one segment of high - conductivity channel, the superposition temperature ratio is 1. Through laboratory experiments, the relationship between the temporary plugging coefficient and the enlarged proportion of the swept volume is obtained, asFigure 10 As shown, the calculated optimal temporary plugging coefficient is about 0.15, and the required amount of temporary plugging agent can be calculated to be 90 cubic meters;

[0140] Step 3: The length of the high-permeability channel is less than 50 m, and the viscosity of the crude oil in Reservoir A is 50,000 - 70,000 mPa·s. Therefore, an organic temporary plugging agent is selected;

[0141] Step 4: Using the numerical simulation method, the injection volume of the second steam slug is optimized to 1200 t, as Figure 11 shown;

[0142] Step 5: After soaking the well for 3 days, the temporary plugging agent fails and the well is opened for production;

[0143] Step 6: After the oil production rate drops to 1 t / d, steam is reinjected to start cyclic development. The recovery factor within the well control range is expected to be 27.8%, as Figure 12 shown.

[0144] Beneficial effects: Through slug injection, the steam fingering phenomenon is weakened and mainly concentrated in the near-wellbore area. Directionally injecting the temporary plugging agent can effectively increase the swept volume of the injected steam, improve the thermal efficiency, and improve the development effect of steam stimulation. The present invention can effectively increase the recovery factor of shallow extra-heavy oil reservoirs, forming a method for improving the development effect of shallow extra-heavy oil reservoirs by directional temporary plugging.

[0145] The above specific implementation manners further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the steam huff-and-puff development effect of shallow ultra-heavy oil reservoirs. It is characterized in that The improvement method includes: Step S1, optimizing the steam injection amount of slug 1, and injecting the first steam slug into the oil reservoir; Step S2, judging the position of the high conductivity channel and calculating the temporary plugging agent requirement according to the bottom hole temperature measurement curve; Step S3, selecting the type of temporary plugging agent and directionally injecting the temporary plugging agent into the oil reservoir; Step S4, optimizing the steam injection rate of the second slug, and injecting a second steam slug into the oil reservoir; Step S5, soaking the well, waiting for the temperature field to expand and the temporary plugging agent to become ineffective, and then switching to production; Step S6, taking the daily oil production as the cut-off condition, performing cycle production.

2. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 1, It is characterized in that The step S1, optimizing the steam injection amount of the first slug, injecting the first steam slug into the oil reservoir specifically comprises: The reservoir properties of the target block were collected, a numerical simulation model was established, and the injection rate of the first steam slug was optimized using thermal efficiency as the evaluation criterion.

3. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 2, It is characterized in that The calculation method of the thermal efficiency is: where x, y, and z are the number of grids in the horizontal, vertical, and longitudinal directions of the numerical model, is the porosity of the grid at any position, S wijk , S oijk , S gijk are the water saturation, oil saturation, and gas saturation at any position, c w , c o , c g , c r are the specific heat capacities of water, oil, gas, and the rock skeleton, V ijk is the volume of the grid at any position, T ijk is the temperature of the grid at any position, T 0 is the original temperature of the oil reservoir, T s is the steam temperature, a is the steam quality, L v is the latent heat of vaporization of steam, V w is the equivalent volume of injected steam water.

4. The method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 1, It is characterized in that The step S2, judging the position of the high conductivity channel and calculating the temporary plugging agent requirement according to the bottom hole temperature measurement curve, specifically includes: According to the bottom hole temperature curve after the steam injection in step S1, the position of the high conductivity channel is determined, and the required amount of temporary plugging agent at different positions is calculated.

5. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 4, It is characterized in that Determining the location of the high-conductivity channel specifically includes: There is a temperature inflection point between the peak and trough of the temperature curve. Take several points near the inflection point of the curve and draw the curve segment M n N n , and record the corresponding abscissa as [i n , i n ’], and perform regression fitting on the line segment. The regression function is as follows: f n f(i) = ax 3 + bx 2 + cx + d (2) Among them, a, b, c, and d are dimensionless coefficients obtained by relevant data fitting software; Obtain curve segment M 1 N 1 On [i n , i n ’], the curvature K n , and the calculation formula is as follows: Obtain the curve segment M 1 N 1 The abscissa i corresponding to the maximum curvature value on nmax ; The method of obtaining the solution is to use a function first derivation method or a mathematical optimization algorithm; If n horizontal coordinates are obtained on the temperature curve, there are n+1 sections in the steam injection process, wherein the region with the temperature peak has m high-conductivity channels, where m is equal to n / 2 or (n+1) / 2.

6. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 4, It is characterized in that The calculation of the demand for temporary plugging agents at different locations specifically includes: Integrate the temperature curve sections where the high-conductivity channels are located respectively; Each temperature curve contains multiple temperature measurement points, which is equivalent to the differentiation of the temperature curve. The temperature measurement point data is accumulated to obtain the superimposed temperature of the section. The calculation formula is as follows: Among them, T j is the temperature at the temperature measurement point, and T 0 is the original temperature of the oil reservoir.

7. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 6, It is characterized in that The integrating the temperature curve segments where the high-conductivity channels are located also includes: Perform regression fitting on the curve segments where the high-diversion channels are located respectively, denoted as function F m (i), and then perform definite integration on the regression formula using mathematical methods to obtain the superimposed temperature of this segment. The calculation formula is as follows: According to the integration results, the proportion of each superposition temperature is calculated. The calculation formula is as follows: Combined with the steam injection volume of segment plug 1, the temporary plugging agent requirement of each segment is calculated using the following formula: V i = x i β max V w (7) Among them, β max is the optimal temporary plugging coefficient, and V w is the slug one steam injection volume.

8. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 6, It is characterized in that The optimal temporary blocking coefficient is obtained through indoor physical simulation, which specifically includes: Oil samples from the target reservoir were selected to carry out a two-dimensional visualization experiment. After a steam slug was injected, different amounts of temporary plugging agents were injected respectively. The ratio of the temporary plugging amount to the volume of the first steam slug was the temporary plugging coefficient. The proportion of the second steam slug volume expansion in different experimental schemes was statistically analyzed to select the optimal temporary plugging coefficient.

9. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 6, It is characterized in that The method for selecting the optimal temporary blocking coefficient is: The steam wave and volume expansion ratio under different temporary plugging coefficients are collected, and the regression fitting formula is as follows: f(β)=eln(β)+g (8) Among them, e and g are dimensionless coefficients, which are obtained by relevant data fitting software; Obtain the curvature K on the curve β , and the calculation formula is as follows: The abscissa β corresponding to the maximum curvature value on the curve max is the optimal temporary plugging coefficient; the calculation method uses the first derivative method of the function or the mathematical optimization algorithm for solution.

10. The method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 1, It is characterized in that In step S3, the type of temporary plugging agent is selected, and the directional injection of the temporary plugging agent into the oil reservoir specifically includes: According to the crude oil viscosity and the high conductivity channel size calculated in step 2, the type of temporary plugging agent is selected, the required amount of high conductivity channel plugging agent is calculated according to step S2, and the temporary plugging agent is directionally injected into the n-1 section using a packer, and the injection order is from the bottom of the well to the wellhead.

11. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 10, It is characterized in that The screening method of the temporary plugging agent comprises: A numerical model of shallow ultra-heavy oil at a certain viscosity was established. By adjusting the reservoir heterogeneity, high conductivity channels of different scales were constructed. Inorganic temporary plugging agents, organic temporary plugging agents, and inorganic temporary plugging agents + organic temporary plugging agents were injected respectively. The plugging effects and investment costs were compared to obtain the best temporary plugging agent at the corresponding scale. By changing the viscosity of crude oil and repeating the relevant calculations, the optimal temporary plugging agent under different viscosities and different high-conductivity channel scales can be obtained.

12. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 1, It is characterized in that The step S4, optimizing the steam injection amount of the second slug, and injecting the second steam slug into the oil reservoir specifically comprises: optimizing and calculating the steam injection amount of the second slug by a numerical simulation method, and selecting the periodic oil production as the evaluation standard.

13. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 1, It is characterized in that The step S5, soaking the well, waiting for the temperature field to expand and the temporary plugging agent to become ineffective, and then switching to production specifically includes: The well is shut down and kept warm, waiting for the mass and heat transfer between the steam and the reservoir, and for the temporary plugging agent to become ineffective. Generally, the well is shut down for 2 to 5 days, and then the well is opened for production.

14. A method for improving the steam stimulation development effect of a shallow ultra-heavy oil reservoir according to claim 1, It is characterized in that The step S6, taking the daily oil production as the cut-off condition, and carrying out the cycle production specifically includes: taking the daily oil production as the production cut-off condition, selecting 1-2t / d, and then injecting steam to carry out the next cycle development.

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