Method for improving cementing quality of sandstone high water cut adjustment well

Abstract

The present application belongs to the technical field of oil and gas exploration and development, and particularly relates to a method for improving cementing quality of sandstone high water cut adjustment well. The method comprises the following steps: 1) before cementing, stopping production and injection of adjacent well; 2) before cementing, judging the density of drilling fluid absolute pressure stability; 3) before cementing, setting drilling fluid performance; 4) during cementing, setting construction discharge and wellbore dynamic equivalent; 5) after cementing, setting cement slurry strength rising time. The present application can greatly improve the cementing quality of sandstone high water cut adjustment well, prevent interlayer cross flow, realize fine layered development and evaluation of old well, improve single well production life and economic benefit, and prolong the development period of old oilfield.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development technology, and specifically relates to a method for improving the cementing quality of sandstone high water-cut adjustment wells. Background Technology

[0002] Cementing is a crucial step in oil and gas well construction, and its quality directly affects well productivity and lifespan. In the mid-to-late stages of development of sandstone oil and gas reservoirs in older oilfields, the well network becomes increasingly dense, and production and injection volumes rise daily. This leads to significant changes in the original formation pressure system and geological properties, primarily manifested in increased heterogeneity, disordered pressure systems, coexistence of high and low pressure zones, decreased oil and gas saturation, increased water cut, increased porosity, enhanced connectivity, and improved permeability. In short, the formation properties have transformed from pure oil and gas layers into high, medium, and low water-bearing layers, or even water-flooded or violently water-flooded layers. Furthermore, some oil and gas reservoirs suffer from inherent structural defects such as folds, faults, fractures, caves, and rock barriers, further complicating the geological and engineering conditions of older oilfields and increasing development difficulties.

[0003] For the reasons mentioned above, older oilfields characterized primarily by deteriorating formation conditions place more stringent demands on cementing quality. The objectives of ensuring cementing quality in older oilfields are as follows:

[0004] (1) Prevent cross-contamination between layers during injection and production;

[0005] (2) Ensure meticulous, tiered development;

[0006] (3) Accurately conduct single-layer geological evaluation;

[0007] (4) Reduce the water content of the produced fluid during injection and production;

[0008] (5) Extend the lifespan of oil and gas wells and increase the value of industrial development.

[0009] However, ensuring cementing quality under complex development conditions is challenging, especially preventing inter-layer water channeling, a common technical problem faced by old oilfields worldwide. Currently, technologies related to improving cementing quality in adjustment wells include CN113698919A, which discloses a thixotropic gelling system suitable for cementing adjustment wells in old oilfields; and CN110846007A, which discloses a latex-based anti-channeling cement slurry system for cementing adjustment wells. These technologies primarily focus on altering the properties of the cement slurry, such as its interfacial bonding properties, the density of the cement stone, its internal crystal structure, and its strength development rate. While these efforts have yielded some results in improving the cementing quality of adjustment wells, the cement slurry itself is a product of cement hydration, and its hydrophilicity is difficult to change. Density and pressure differences exist between formation water and cement slurry, making liquid replacement unavoidable. The inconsistent mineralization of formation water and cement slurry, along with significant differences in ion types and concentrations, makes interfacial ion exchange inevitable. Pressure changes in the wellbore during cementing operations and the waiting period for setting can cause cement slurry filtrate to permeate to the formation interface. All of the above reasons cause the cement slurry at the sandstone formation interface to be in a dynamic, waiting-to-set state, making it difficult to guarantee the quality of interface bonding. Therefore, addressing the cement slurry itself alone cannot completely solve the problem. This invention, however, solves the cementing quality problem in high water-cut sandstone oil and gas reservoirs from the source, which is of great significance for extending the production life of old oilfields. This invention can effectively improve the cementing quality of high water-cut sandstone oil and gas layers, achieving effective interlayer sealing, and is one of the important means to extend the production life of high water-cut adjustment wells and even the entire old oilfield. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a method for improving the cementing quality of sandstone high water-cut adjustment wells. This invention can significantly improve the cementing quality of sandstone high water-cut adjustment wells, prevent inter-layer cross-contamination, enable precise stratified development and evaluation of old wells, increase the production life and economic benefits of single wells, and extend the development period of old oilfields.

[0011] The technical solution provided by this invention is as follows:

[0012] A method for improving cementing quality in sandstone high-water-cut conditioning wells includes the following steps:

[0013] 1) Before cementing, production and injection in adjacent wells should be stopped;

[0014] 2) Before cementing, determine the absolute pressure-stable density of the drilling fluid;

[0015] 3) Before cementing, set the drilling fluid properties;

[0016] 4) During cementing, set the construction displacement and wellbore dynamic equivalent;

[0017] 5) After cementing is completed, set the cement slurry strength initiation time.

[0018] Based on the above technical solutions, the pressure difference in the wellbore during cementing and the waiting period for cement slurry to set (the difference between the hydrostatic pressure in the wellbore and the formation pressure) is reduced, thus minimizing the diversion effect of the wellbore fluid at the high-permeability interface. A short transition time is set for the cement slurry to reduce density difference displacement and ion exchange efficiency. During cementing operations and the waiting period for cement slurry to set, surrounding production wells are shut down. These measures can achieve static setting of the cement slurry at the high-permeability formation interface, ensuring cementing quality.

[0019] Specifically, step 1) includes the following steps: before drilling to expose the target layer, the injection wells in the same layer within a 500m radius of the target layer of the drilling well are stopped and the pressure is reduced to within 2MPa; before cementing construction, the production wells in the same layer within a 500m radius of the target layer are stopped before the casing is installed; production is resumed after the cement slurry has set, ensuring that the cement slurry sets and develops its strength under static conditions.

[0020] Specifically, step 2) includes the following steps:

[0021] 201) The wellbore remains in a stationary state for more than 12 hours during tripping or tripping;

[0022] 202) After drilling is completed and the pump is started to circulate the outer annulus, observe the changes in the properties of the drilling fluid injected into and returned to the wellhead within a certain time delay.

[0023] 203) If the density at the drilling fluid outlet and inlet remains unchanged, and there are no sudden changes in rheological properties such as viscosity and shear stress;

[0024] 204) If step 203) meets the conditions, then it is determined that: there is no water intrusion or oil and gas intrusion during the entire process of tripping and standing still, the drilling fluid in the whole wellbore is not contaminated, and the sub-density drilling fluid can achieve pressure stabilization.

[0025] Preferred: In step 203: the difference is ≤0.01 g / cm³ 3 Viscosity change ≤ 2s; shear stress change ≤ 0.5pa.

[0026] Specifically, step 3) includes the following steps:

[0027] 301) Adjust the drilling fluid properties to achieve a saka soil content ≤50g / L, a drilling fluid solid content ≤25%, a good rheological n value ≥0.72, and a filter cake thickness ≤1mm;

[0028] 302) High-volume circulating well washing, using high-return-speed well washing, ensures that residual mud cake, rock cuttings and gravel adhering to the well wall and casing wall can be carried from the bottom of the well to the surface.

[0029] Based on the above technical solution, a dense impermeable membrane is formed on the interface of a high-permeability formation (such as sandstone) before cementing, which prevents the wellbore fluid and formation fluid from contacting and interacting during cementing and waiting for solidification, thereby achieving static solidification and improving the bonding strength of the high-permeability production layer interface.

[0030] The aforementioned dense, impermeable membrane is formed by increasing the drilling fluid density before running the casing to stabilize the production formation pressure. Under the action of high pressure differential, the drilling fluid forms a dense, high-strength filter cake that seals the sandstone production formation with high water content and high permeability, blocking the passage between the formation and the wellbore.

[0031] Preferred:

[0032] In step 301): the drilling fluid comprises the following components by weight percentage: 2%–4% bentonite, 0.3%–0.8% caustic soda, 3%–5% filtration reducing agent, 0.5%–2.0% lubricant, 1.5%–2.5% inhibitor, 2.5%–3.5% plugging agent, barite, and water;

[0033] In step 302): the annular return velocity in the wellbore is ≥1.2m / s, or the flow is turbulent.

[0034] Specifically, in step 4):

[0035] Set the construction flow rate to ensure that the annular return velocity in the wellbore is ≤0.4m / s, or that it is a plug flow.

[0036] Set the wellbore dynamic equivalent, the bottom dynamic equivalent a1 during the pre-cementing circulation, and the bottom dynamic equivalent a2 during the pre-filling fluid and cement slurry injection process, ensuring that a2-a1≤0.05g / cm=3, thereby reducing the probability of wellbore fluid deflection at high-permeability interfaces.

[0037] Specifically, step 5) includes the following steps:

[0038] 501) Adopt a short-setting cement grout system and select a static cementitious strength transition time ≤ 5min to reduce the chance of water intrusion;

[0039] 502) The thickening time to reach a consistency of 100 BC. Thickening time = construction time + 30 to 60 minutes. This reduces the liquid settling time of the cement slurry and decreases the chance of it being replaced by formation water.

[0040] 503) Multi-setting cement grout system to achieve pressure stabilization of high-permeability sandstone layers during weight loss.

[0041] Preferred:

[0042] In step 501), the static gel strength transition time is the time required for the gel value to increase from 48 Pa to 240 Pa.

[0043] In step 503), the multi-setting cement slurry system refers to the wellbore sealing section where there are two or more types of cement slurry.

[0044] Preferred:

[0045] In step 501), the method for shortening the static cementitious strength transition time of cement slurry is selected from: reducing the liquid-to-solid ratio, adding 3% to 6% silica fume to the cement slurry, and adding 1% to 4% cement accelerator.

[0046] In step 502), the method for adjusting the thickening time is selected from: increasing or decreasing the retarder.

[0047] In the above technical solution:

[0048] 1) Old standards and judgment principles: Add 0.05 to 0.10 g / cm³ to the reservoir pressure coefficient. 3 The air layer pressure coefficient is increased by 0.07 to 0.15 g / cm³. 3 On this basis, exceeding the collapse pressure can suppress wellbore collapse. However, this principle is far from sufficient for cementing high-water-cut, high-permeability sand layers.

[0049] Based on the above technical solution, if the wellbore remains in a static state for more than 12 hours after drilling is completed and the pump is turned on to circulate the outer annulus for a delay period of time, the density of the drilling fluid at the inlet and outlet will not change, and the rheological indicators such as viscosity and shear force will not change abruptly. That is, there will be no water intrusion or oil and gas intrusion during the entire process of drilling and static operation, and the drilling fluid in the entire wellbore will not be contaminated in any way, thus achieving pressure stabilization.

[0050] 2) Drilling fluid properties before cementing

[0051] It has low saka soil content (≤50g / L), low drilling fluid solid content (≤25%), good rheological properties (n value ≥0.72), and thin and tough filter cake (cake thickness ≤1mm).

[0052] 3) Density difference setting during cementing operations and waiting period

[0053] High-volume, high-return-velocity well washing is employed to ensure wellbore cleanliness. While considering displacement efficiency, low-volume, low-return-velocity plug flow displacement is used as much as possible to reduce the dynamic and static equivalent density difference in the wellbore and prevent leakage of high-permeability layers.

[0054] Taking into account both replacement efficiency and cement paste performance, a cement paste of appropriate density (0.12 g / cm³) should be used. 3 ≤Cement slurry density - Drilling fluid density≤0.50g / cm³ 3 This reduces the pressure difference before and after weightlessness.

[0055] 4) Cement grout performance settings

[0056] Short transition time: The time required for static gel strength to reach 48–240 Pa, with a recommended transition time T ≤ 5 min, to control water channeling height;

[0057] Short setting time: Thickening time within 100 Bc, recommended T = construction time + 30 to 60 min, to reduce the liquid standing time of cement slurry and reduce the chance of replacement with formation water;

[0058] A multi-stage cement grouting system was set up to achieve pressure stabilization of the high-permeability sandstone layer during weight loss.

[0059] 5) Measures to suspend mining and injection

[0060] For injection wells within 500m of the target layer of the construction well, injection should be stopped before drilling to expose the target layer, and the pressure should be reduced to within 2MPa; for production wells within 500m of the target layer of the construction well, production should be stopped before casing is installed; production should be resumed after the cement slurry has set, to ensure that the cement slurry sets and develops its strength under static conditions.

[0061] The beneficial effects of this invention are as follows:

[0062] 1) It can effectively solve the cementing quality problem of adjustment wells in high water-cut and high permeability sandstone formations, prevent inter-layer cross-contamination, realize fine-grained stratified development and evaluation of old wells, improve the production life and economic benefits of single wells, and extend the development period of old oilfields.

[0063] 2) The process mechanism is simple, easy for on-site engineering technicians to master, highly operable on-site, and the drilling and completion process remains unchanged.

[0064] 3) No special requirements are placed on drilling and cementing equipment, the injection and displacement parameters are set more scientifically and reasonably, and the operation compliance rate is high.

[0065] 4) The supporting processes involve conventional drilling and completion operations.

[0066] 5) The supporting process methods do not use new materials or tools, do not add safety risks, do not increase costs, and are economical and applicable. Attached Figure Description

[0067] Figure 1 This is a schematic diagram of the static setting of cement slurry.

[0068] Figure 2 The first part of the image shows the cementing quality of well Zao 1266-24.

[0069] Figure 3 The latter part of the image shows the cementing quality of well Zao 1266-24.

[0070] Figure 4 The first part of the image shows the cementing quality of well Zao 1266-14.

[0071] Figure 5 The latter part of the image shows the cementing quality of well Zao 1266-14.

[0072] Figure 6 The first part of the image shows the cementing quality of well 38-17.

[0073] Figure 7 The latter part of the diagram shows the cementing quality of well 38-17.

[0074] Figure 8 The first part of the image shows the cementing quality of well 39-11.

[0075] Figure 9 The latter part of the diagram shows the cementing quality of well 39-11.

[0076] Figure 10 The first part of the image shows the cementing quality of well 39-12.

[0077] Figure 11 The latter part of the diagram shows the cementing quality of well 39-12. Detailed Implementation

[0078] The principles and features of the present invention are described below. The embodiments given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the test methods used in the embodiments are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0079] Example 1

[0080] In the Zao 1266 fault block of Dagang Oilfield, the cementing quality was significantly improved after applying the engineering method of this invention. The target formations of the Zao 1266 fault block are the Zao IV and Zao V oil groups, buried at depths of 1738-2100m. These formations consist of alternating mudstone and sandstone, are relatively thin, and are all water-flooded layers with severe heterogeneity and highly uneven permeability, with high and low permeability layers coexisting, and permeability ranging from 50 to 2000 × 10⁻⁶. -3 μm 2 190×10 -3 μm 2 With an average porosity of 22.0%, and after more than 30 years of water injection and mining, the pore throats in the strata are uneven in size, highly interconnected, and prone to sudden flooding.

[0081] The drilling fluid density after drilling the fault block was 1.18-1.20 g / cm³. 3 The drilling fluid density before cementing is 1.18-1.49 g / cm³. 3 Before implementing absolute pressure stabilization measures, and with all other operating conditions unchanged, the cementing quality significantly improved, with the section length qualification rate increasing from a minimum of 40.96% to a maximum of 99.18%. The current absolute pressure stabilization drilling fluid density for this fault block should be 1.40 g / cm³.3 That concludes the discussion. The properties of the cement slurry in this block remained largely unchanged before and after cementing; therefore, the absolute stabilization of the high-permeability producing formation by the drilling fluid before cementing is crucial.

[0082] Statistical data related to the cementing quality of fault-block wells are shown in Appendix 1; the cementing quality qualification rate of well Zao 1266-24 is 40.96%, see Appendix 1. Figure 2 , 3 The cementing quality qualification rate of well Zao 1266-14 was 99.18%, see attached. Figure 4 , 5 .

[0083] Example 2

[0084] In the Kou 11 block of Dagang Oilfield, the cementing quality problem of the producing formation was completely solved after adopting the engineering methods of this invention. The target formation in the Kou 11 block is a Permian sandstone formation, buried at a depth of 1630-1900m, with an average permeability of 520×10⁻⁶ m. -3 μm 2 With an average porosity of 28.0%, after years of water injection development, due to uneven water injection, water-flooded layers and pressure-deficient layers coexist, and severe well leakage and water intrusion occur frequently.

[0085] Due to severe formation energy depletion and insufficient pressure bearing capacity, the drilling fluid density before cementing in this fault block was 1.15-1.16 g / cm³. 3 The drilling fluid inlet and outlet density difference was zero, achieving absolute pressure stabilization before cementing. However, due to unreasonable cement slurry density and injection / displacement parameter settings, under high permeability conditions, the equivalent density difference in the wellbore was large during the dynamic and static cementing process and the weight loss period after setting. This led to fluid interface diversion and ion exchange, resulting in poor cementing quality in the early stages of well 38-17. The three wells adopted the engineering method provided by this invention, reducing the cement slurry density and the injection / displacement rate during cementing construction, significantly improving cementing quality and achieving excellent results.

[0086] Cementing quality statistics are shown in Appendix 2; for poor cementing quality in well 38-17, see Appendix 38-17. Figure 6 , 7 The cementing quality of well 39-11 is excellent; see attached. Figure 8 , 9 The cementing quality of well 39-12 is excellent; see attached document. Figure 10 , 11 .

[0087] Table 1: Statistics on Cementing Quality Before and After Absolute Pressure Stabilization in the Zao 1266 Fault Block

[0088]

[0089]

[0090] Table 2: Cementing Quality Statistics for Block 11

[0091]

[0092] like Figure 1 The diagram shown is a schematic of the static setting of cement slurry, in which:

[0093] Stabilizing cement slurry: In multi-stage cement slurry systems, it is not responsible for sealing sandstone layers, but for providing hydrostatic pressure to the bottom of the well;

[0094] Absolutely stabilized mud cake: Drilling fluid flows in the annulus and forms a mud cake in the formation through re-permeation and adsorption. By optimizing the thickness, toughness, and composition of the mud cake, an "absolutely stabilized mud cake" is ultimately formed, which can block and seal oil, gas, and water in the formation.

[0095] Interlayer: A dense stratum that can block oil, gas and water from moving vertically between strata;

[0096] High water content and high permeability sandstone layer: A type of sandstone stratum with very high permeability and high water content, which easily leads to liquid and ion exchange between cement slurry and the stratum, thus damaging the sealing effect of the cement ring;

[0097] Cement grout for production layer: In a multi-stage cement grout system, the cement grout section is specifically designed to seal the production layer.

[0098] Figures 2 to 11 middle:

[0099] The upper part of the image shows red and red-white markings, which indicate that the strata contain oil, gas, water, etc.

[0100] The middle part of the diagram represents cementing quality; dark shades indicate good cementing quality, while white areas without shades indicate...

[0101] From the red and white mixed sections and the corresponding cementing quality, one can determine the quality of cementing in the well section corresponding to the oil, gas and water layers.

[0102] From the appendix Figure 1 As can be seen, the cementing quality of the oil, gas and water layers is poor, indicating that the cement slurry has not properly sealed the oil, gas and water.

[0103] From the appendix Figures 2-11 As can be seen, the cementing quality of oil, gas and water formations is significantly improved by using the method and process provided by this invention, indicating that the method and process provided by this invention can improve the cementing quality of sandstone high water-cut adjustment wells.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving cementing quality in sandstone high-water-cut adjustment wells, characterized in that, Includes the following steps: 1) Before cementing, production and injection in adjacent wells should be stopped; 2) Before cementing, determine the absolute pressure-stable density of the drilling fluid; 3) Before cementing, set the drilling fluid properties; 4) During cementing, set the construction displacement and wellbore dynamic equivalent; 5) After cementing is completed, set the cement slurry strength initiation time.

2. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that, Step 1) includes the following steps: Before drilling to expose the target layer, the injection wells in the same layer within a 500m radius of the target layer of the drilling well are stopped and the pressure is reduced to within 2MPa; before cementing construction, the production wells in the same layer within a 500m radius of the target layer are stopped before the casing is installed; after the cement slurry has set, production is resumed to ensure that the cement slurry sets and develops its strength under static conditions.

3. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that, Step 2) includes the following steps: 201) The wellbore remains in a stationary state for more than 12 hours during tripping or tripping; 202) After drilling is completed and the pump is started to circulate the outer annulus, observe the changes in the properties of the drilling fluid injected into and returned to the wellhead within a certain time delay. 203) If the density at the drilling fluid outlet and inlet remains unchanged, and there are no sudden changes in viscosity and shear rheological properties; 204) If step 203) meets the conditions, then it is determined that: there is no water intrusion or oil and gas intrusion during the entire process of tripping and standing still, the drilling fluid in the whole wellbore is not contaminated, and the sub-density drilling fluid can achieve pressure stabilization.

4. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 3, characterized in that: In step 203: the difference is ≤0.01g / cm 3 Viscosity change ≤ 2s; shear stress change ≤ 0.5pa.

5. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that, Step 3) includes the following steps: 301) Adjust the drilling fluid properties to achieve a saka soil content ≤50g / L, a drilling fluid solid content ≤25%, a good rheological n value ≥0.72, and a filter cake thickness ≤1mm; 302) High-volume circulating well washing, using high-return-speed well washing, ensures that residual mud cake, rock cuttings and gravel adhering to the well wall and casing wall can be carried from the bottom of the well to the surface.

6. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 5, characterized in that: In step 301): the drilling fluid comprises the following components by weight percentage: 2%–4% bentonite, 0.3%–0.8% caustic soda, 3%–5% filtration reducing agent, 0.5%–2.0% lubricant, 1.5%–2.5% inhibitor, 2.5%–3.5% plugging agent, barite and water to the preset density; In step 302): the annular return velocity in the wellbore is ≥1.2m / s, or the flow is turbulent.

7. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that, In step 4): Set the construction flow rate to ensure that the annular return velocity in the wellbore is ≤0.4m / s, or that it is a plug flow. Set the wellbore dynamic equivalent, the bottom dynamic equivalent a1 during the pre-cementing circulation, and the bottom dynamic equivalent a2 during the pre-filling fluid and cement slurry injection process, ensuring that a2-a1≤0.05g / cm=3, thereby reducing the probability of wellbore fluid deflection at high-permeability interfaces.

8. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that, Step 5) includes the following steps: 501) Adopt a short-setting cement grout system and select a static cementitious strength transition time ≤ 5min to reduce the chance of water intrusion; 502) The thickening time to reach a consistency of 100 BC. Thickening time = construction time + 30 to 60 minutes. This reduces the liquid settling time of the cement slurry and decreases the chance of it being replaced by formation water. 503) Multi-setting cement grout system to achieve pressure stabilization of high-permeability sandstone layers during weight loss.

9. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that: In step 501), the static gel strength transition time is the time required for the gel value to increase from 48 Pa to 240 Pa. In step 503), the multi-setting cement slurry system refers to the wellbore sealing section where there are two or more types of cement slurry.

10. The method for improving cementing quality in sandstone high water-cut adjustment wells according to claim 1, characterized in that: In step 501), the method for shortening the static cementitious strength transition time of cement slurry is selected from: reducing the liquid-to-solid ratio, adding 3% to 6% silica fume to the cement slurry, and adding 1% to 4% cement accelerator. In step 502), the method for adjusting the thickening time is selected from: increasing or decreasing the retarder.

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