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Influence of Drilling Fluid Properties on Cementing Quality of Water-flooded Layer

2022-06-24

This paper focuses on the influence of drilling fluid properties on the cementing quality of water-flooded layers, trying to improve the cementing quality of water-flooded layers by strengthening the relevant properties of drilling fluids and improving drilling fluid technology. Through the research, the basic conclusions are: ①The performance of drilling fluid is very important to control the cementing quality of the water-flooded layer cementing interface; ②The main performance that affects the cementing quality of the water-flooded layer is the filtration and wall-building performance of the drilling fluid. The formation of dense, tough and low permeability mud cake in the sealing section of the water-flooded layer can effectively reduce the adverse effect of the water-flooded layer on the cementing quality; (3) In order to ensure the cementing quality of the water-flooded layer, drilling should be carried out in the water-flooded layer block. In the whole process of well-completion and well-completion, high-quality drilling fluid system with strong inhibition and good wall-building performance is used, and the performance is carefully maintained. It can reduce the adverse effect of drilling fluid on the cementing quality of the sealing interface, increase the reactivity of the sealing surface, and compact the cementing interface, thereby improving the cementing quality of the water-flooded layer.

 

Improving the cementing quality of the water-flooded layer has always been a technical problem in cementing engineering. For water-flooded layer cementing, the impact of drilling fluid on cementing quality is very obvious. In order to improve the cementing quality of water-flooded layer, it is very important to improve the performance of drilling fluid. This is because, if the static pressure or resistance capacity of the annular medium is lower than the formation pore pressure of the water-flooded layer after the cementing operation, the formation fluid will first destroy the filter cake of the drilling fluid, and then enter the annular space, which will cause damage to the formation fluid. The quality of cementing and cementation has an adverse effect. It can be seen that the high-pressure water in the flooded layer can only have a corresponding destructive effect through the damaged filter cake channel. If the filter cake is not damaged, the seepage of the formation water will encounter resistance, and its destructive effect will be greatly reduced. , the cement slurry can be solidified normally, and it is difficult to generate micro-cracks at the cemented interface, and the sealing quality of the water-flooded layer may be guaranteed. Through research, Gong Yujie et al. found that when serious cementing quality problems occur, the pressure of the fluid in the formation must first destroy the filter cake, and then cause other problems. The filter cake has a good resistance to the external channeling of the interlayer liquid. ability. Therefore, the mud cake formed by the drilling fluid in the permeable formation is an important barrier to prevent the formation water from invading the wellbore in the water-flooded formation. Therefore, we must pay attention to the influence of drilling fluid performance on formation water seepage when analyzing the influence of formation water seepage in water-flooded layers on cementing quality. The purpose of improving the cementing quality of the water-flooded layer is achieved by strengthening the performance of the drilling fluid. In this paper, the influence of drilling fluid performance on formation water seepage and cementing quality of water-flooded layer will be studied, and a drilling fluid technical scheme that can improve the cementing quality of water-flooded layer will be proposed. Another purpose of this study is to further understand the importance of enhancing drilling fluid performance and improving drilling fluid technology to improve cementing quality by studying the effect of drilling fluid on cementing quality of water-flooded layers.

 

Controlling effect of drilling mud cake quality on formation water intrusion in water-flooded formations In order to study the importance of drilling mud cake against formation water intrusion, the formation water permeability resistance test of cores was carried out. The test method is as follows: ① Put the field core into the TY24 high-pressure core holder (produced by Haian, Jiangsu), and first measure the formation water permeability resistance before the formation of the mud cake of the drilling fluid; ② Put the core into the high-pressure curing kettle and put it into the high-pressure curing kettle. The drilling fluid sample tested, pressurized 3.5MPa, and let stand for 1h to form a mud cake on the core surface; ③ Take out the core, remove the mud cake on the side of the core, and then put it into the TY24 high-pressure core holder to make the formation water again penetration resistance. The test results are shown in Table 1, and the drilling fluid formula is as follows.

 

1#3% bentonite slurry

 

2# Tarim Lunnan Well LN2203 Well Slurry (Polysulfone Drilling Fluid)

 

3#1#+0.1%KPAM+0.2%JT2888

 

4#3#+1.2%CMC2LV+2%QS22(particle size is 0.03mm)+1%QS22(particle size is 0.05mm)

 

It can be seen from Table 1: ①Once a mud cake is formed on the wellbore, the permeability resistance of formation water will increase greatly, and the pressure difference required for formation water to penetrate into the wellbore will be greater. The mud cake of the drilling fluid is a reliable barrier to prevent the high pressure water flow from infiltrating the wellbore, which is the basic guarantee of the cementing quality of the water-flooded layer. ②The water loss and wall-building properties of drilling fluids are different, and the resistance to formation water invasion is also different. Tough, dense, low permeability, especially high temperature and high pressure mud cake with low filtration loss can control formation water intrusion better than ordinary drilling fluid mud cake, such as the mud cake of Tarim Lunnan Well LN2203. Therefore, the improvement and control of the mud cake quality of the drilling fluid, especially the control of the high temperature and high pressure fluid loss performance, is very important for the cementing quality of the water-flooded layer. 2 Controlling effect of drilling fluid mud cake quality on cement slurry water loss The drilling fluid mud cake quality is also crucial to the control of cement slurry water loss to the formation, and thus also affects the cementing quality of water-flooded layers. In order to study the control effect of drilling mud cake on the water loss of cement slurry, the tests shown in Table 2 were carried out. The test method is as follows: ① Do the drilling fluid high pressure water loss test in the NF21 drilling fluid mud cake adhesion coefficient tester (Qingdao, Shandong); ② pour out the drilling fluid in the cup, keep the drilling mud cake formed in step 1), and put it in the cup. Cement slurry (grade G oil well cement slurry) was poured into it, and the water loss test of the cement slurry was done. The results are shown in Table 2. It can be seen from Table 2: ① The larger the filtration loss of the drilling fluid, the looser the mud cake, the better the permeability, and the greater the water loss of the cementing fluid to the formation; ② the low water loss and strong wall-building properties High-quality drilling fluids, such as Tarim Lunnan LN2203 and LN2102 muds, can effectively control the water loss of the cementing fluid to the permeable formation and ensure the quality of the interface sealing; Slurry seepage is very important, and the dense and tough mud cake undoubtedly increases the resistance of formation water seepage in the water-flooded layer, which provides a certain guarantee for the improvement of cementing quality. The 5# and 6# drilling fluid formulations in Table 2 are as follows.

 

5#3#+0.8%CMC2LV

 

6# Tarim South Well Slurry (LN2102 Well)

 

Controlling effect of drilling fluid mud cake quality on interface cementation quality

 

In the experiment, the bonding strength of the cementing fluid and the drilling fluid soaked core interface was tested to simulate the cementing strength of the second interface: ① The dry core samples were soaked in the experimental base slurry for 24 hours and numbered respectively; ② After 24 hours, the core samples were taken out and placed vertically Standby after 20min; ③ Put the core treated in step ② vertically into the center of the galvanized steel pipe with an inner diameter of 60 mm and a height of 50 mm sealed with a plastic bag at the lower end; ④ inject cementing fluid (water ash into the annulus between the steel pipe and the core) Jiahua G-grade oil well cement slurry with a ratio of 0.44), the upper surface is flush with the core, and the upper end is sealed and marked; ⑤ Put it in a water bath for curing at 90°C for 24 hours; ⑥ After taking it out, use XAN2JQ interface shear bonding The strength test process measures the interface bonding strength and completes the test. For multifunctional drilling fluids that have been proven to improve the cementing interface strength, the quality of the mudcake of the drilling fluid has a great influence on the cementing strength of the second cementing interface. If the mudcake quality is not good, even if the multifunctional drilling fluid is used , the effect of improving the interfacial bonding strength can not be brought into play, see Table 3. Some drilling fluid formulations in Table 3 are as follows.

 

7#5#+5% slag (particle size is 0.03mm)

 

8#3#+0.4%PAC+1%SMP+2%QS22+1%FT21

 

9#8#+ slag (particle size is 0.03mm)

 

10#3% saline-resistant soil (particle size is 0.10mm)+0.8%PAC+4% sodium silicate 11#10#+5% slag (particle size is 0.03mm)

 

It can be seen from Table 3: (1) In the sandstone formation with good permeability, the correlation between the cementation strength of the two interfaces and the quality of the mud cake is the strongest, more than the correlation with the filtrate of the drilling fluid. Although the water loss of the drilling fluid is small, if the mud cake is thick and the compactness is poor, the bonding strength of the two interfaces is still very low. ②When adding active minerals to drilling fluid, the compatibility with drilling fluid system should be considered. If the compatibility between the active minerals and the drilling fluid system is poor, the mud cake will become thicker and the quality will be deteriorated after the drilling fluid is added, so the interfacial bonding strength of the two interfaces will not be enhanced, but will be reduced. 4 Influence of other influencing factors related to drilling fluid on the cementing quality of water-flooded layers The field cementing examples of adjustment wells have repeatedly shown that if the drilling fluid contains a large amount of bridging and plugging agent particles, thicker particles will form on the well wall. The mud cake has a great influence on the cementing quality, and often leads to unqualified cementing and sealing. Before cementing, the performance of drilling fluid should be adjusted to remove virtual mud cake and clean well wall by circulating well to create favorable conditions for cementing. Whether the wellbore is regular or not has a great influence on the bonding strength of the interface. If the wellbore is irregular, it is easy to accumulate loose drilling cuttings and thick mud in the belly, which cannot be replaced during the cementing process, thus seriously affecting the quality of interface cementation. While drilling in the water-flooded zone, the instability of the wellbore is a serious problem. In order to improve the cementing quality of the water-flooded layer, drilling fluids with strong inhibition and good wall-building properties should be used in the whole well to maintain the regularity of the wellbore and the stability of the wellbore. 5 Effect of surface pretreatment technology on cementing quality of water-flooded layer The second interface of cementing has always been the weak link of cementing quality, especially for water-flooded layer cementing. In order to increase the affinity of the drilling fluid adsorbed on the casing surface and the formed drilling fluid mud cake to the cementing fluid, minimize the adverse effect of the drilling fluid on the cementing quality, and create favorable conditions for improving the cementing quality of the water-flooded layer, there are It is necessary to pre-treat the casing surface and the formed drilling fluid mud cake by using a special latex flushing and spacer fluid during the cementing of the water-flooded layer. The test methods are as follows: (1) The interface bonding strength of cementing-interface is simulated by testing the interface bonding strength of steel pipes soaked in cementing fluid and drilling fluid. The two-interface simulation test method is the same as above; ② Sample maintenance method: make the sample according to the literature [2] and the above-mentioned two-interface simulation test method, then put clean water into the aging tank of the roller heating furnace, put the sample, keep the water full, and cover it tightly Cover, pressurize 2MPa, and cure at 60°C for 24h. The results are shown in Table 4 and Table 5. The cement slurry formula in table 4 is as follows:

 

1′# Oil well cement paste (W/C=0.44)

 

2′#1′#+10% latex (Lanzhou Petrochemical Products)

 

3′#1′#+3% lattice expansion agent (product of Petroleum University)

 

4′#1′#+20% silicon powder (particle size is 0.18mm)

 

The immersion drilling fluid formula is as follows in table 4:

 

12# (Polymer Positive Electrolyte Drilling Fluid) 5#+1% Positive Electrolyte

 

Rinse liquid formula is as follows in table 4:

 

136% latex + 6% microsilicon

 

The drilling fluid formula in table 5 is as follows:

 

13# (polymer drilling fluid) 3#+0.3% CMC2LV

 

14# (polymer mixed oil drilling fluid) 13#+8% crude oil

 

It can be seen from Table 4 and Table 5 that whether it is the mud cake formed by the polymer drilling fluid, the oil-mixed polymer drilling fluid or the positively charged adhesive drilling fluid, the interface bonding strength of the surface pretreated interface is different from that of the interface without surface pretreatment. The bonding strength is obviously improved compared with that, especially the bonding strength of the two interfaces. The mechanism of pretreating the casing surface and the mud cake surface to improve the bonding strength of the interface is that the latex and microsilica act synergistically to adsorb firmly on the treated surface, forming a layer of highly active adsorption layer, which can compact the bonding interface and promote cementing. Hydration reaction of liquid at the mounting interface. Especially at the second interface, due to the formation of micro-silicon and latex films, various unfavorable factors for the hydration reaction on the surface of the mud cake are eliminated through the filling and densification, and the affinity and reactivity of the mud cake and the cementing fluid are increased, and the cementing fluid is improved. A firm bond with the mudcake surface.

 

Formation pretreatment technology of water-flooded layer sealing section

 

The main influence of the water-flooded layer on the cementing quality is that the formation water of the water-flooded layer intrudes into the cementing fluid due to factors such as weight loss and shrinkage of the cement slurry during the solidification process of the cement slurry, forming a channeling channel. Therefore, if the water-flooded layer can be effectively blocked before cementing, and a solid barrier to prevent water flow can be formed in the well section of the water-flooded layer, the influence of water seepage in the water-flooded layer on the cementing quality will be greatly reduced. The formation pretreatment technology is to pre-block the well section of the water-flooded layer in advance before cementing the water-flooded layer, to create conditions for improving the cementing quality of the water-flooded layer, and to solve the problems that may occur in the cementing construction before the casing is placed. . The implementation of formation pretreatment technology depends on the characteristics of the pre-sealed formation, wellbore conditions and drilling operations. Water-flooded layer pretreatment technology can be divided into the following aspects [326]: 1) MTC cementing fluid or cement slurry pretreatment technology. After drilling through the pre-sealing section of the water-flooded layer or before cementing, pump a curable plugging agent in the well section of the water-flooded layer, that is, a mixture of cement slurry and various additives, or MTC sealing liquid, to seal the well wall. reinforcement. 2) Squeeze plugging agent pretreatment method. After drilling through the water-flooded layer or before cementing, prepare a special plugging fluid, replace it in the well section of the water-flooded layer, and then slowly squeeze it into the formation with small displacement and low pump pressure to prepend the well section of the water-flooded layer. The treatment is pre-plugging, which can reduce the influence of the water-flooded layer on the cementing quality during cementing. This method is similar to the pre-plugging technique during drilling. 3) Chemical pretreatment method. The purpose of using chemical pretreatment method is to reduce the hydration activity of mudstone, increase the hydrophobicity of the wellbore composed of argillaceous rock, strengthen the unstable formation that is easy to hydrate and expand, and create favorable conditions for interface cementation. This process is based on reducing the hydration activity of mudstone, and pretreatment with strong inhibitory chemical solutions, such as quaternary amine aqueous solution and other cationic polymer electrolyte aqueous solutions, ensures the regularity of well diameters and improves the Cementing quality. 7 Conclusion 11 The performance of drilling fluid, mainly the filtration and wall-building performance of the drilling fluid, has an important influence on the control of the cementing quality of the water-flooded layer. Good mud cake quality can not only keep the well diameter regular, but also form a reliable barrier to prevent the water seepage in the water-flooded layer in the well section, and reduce the adverse effect of the water-flooded layer on the cementing quality. Therefore, in order to solve the problem of the cementing quality of the water-flooded layer, it is necessary to use a drilling fluid system with good wellbore stability and good mud cake quality in the drilling process to ensure the formation of compact, tough and strong wall-building properties in the sealing section of the water-flooded layer. , The mud cake with low permeability, strictly control the filtration performance of high temperature and high pressure. It is impossible to fundamentally improve the cementing quality of the water-flooded layer without paying attention to the quality of the drilling fluid in the water-flooded layer. 21 For the water-flooded layer with serious water flooding, high water content and high pressure, and the quality of cementing and sealing is difficult to guarantee, it is recommended to use the pre-treatment process of the cementing surface, and use new processes such as latex to wash the spacer before cementing. Pretreatment can reduce various harmful factors that are unfavorable to the interface cementing quality, increase the affinity and reactivity of the cementing surface and the cementing fluid, and ensure the cementing quality of the well section of the complex water-flooded layer. 31 In the process of drilling the water-flooded layer, high-quality drilling fluid should be used, the performance of the drilling fluid should be carefully maintained, a stable and regular bonding interface should be provided for cementing, and the technical management of the drilling fluid should be regarded as an important part of the completion system engineering. For complex wells with severe flooding, poor wellbore stability, and easy leakage and collapse, the wellbore reinforcement technology should be implemented before cementing to create good conditions for cementing the water-flooded layer.