The new ICS can change the oil-based mud in the channeling channel and possibly improve the hydraulic sealing ability of the oil well. Its effect is far better than that achieved only by removing the mud.

At present, most horizontal wells in the United States adopt multi-level stimulation measures. In order to increase production effectively, it is necessary to isolate each well section inside and outside the production casing. In the casing, the cement must be able to form an external isolation, although the bridge plug can be used between the well sections to form an effective sealing. According to the design, it is difficult to optimize all design parameters to achieve the best cementing operation. Moreover, few operators are engaged in horizontal cementing quality logging, and the channeling in the annulus is often considered as the root cause of low production efficiency. Since completion efficiency and well productivity depend on good interlayer isolation, it is generally believed that the profitability of the well is also affected.

Mud removal is still an integral part of cementing operations. A new cement formula has been developed in the industry, which can improve the isolation effect between layers under the condition of poor mud removal. ICS can react with hydrocarbon in oil-based drilling fluid, reduce the permeability and fluidity of channeling channel, and improve the possibility of hydraulic isolation. In addition, a special test protocol is developed to demonstrate the function of the new system. In addition, API test method and analysis technology are used to optimize the cement slurry.

For decades, the industry has been trying to improve the cementing quality by optimizing the design standards discussed above, but a new idea needs to be changed. ICs is developed according to the idea of transforming the residual oil-based drilling fluid into plugging material. This system strengthens the effect of interlayer isolation in the remaining well section of oil-based drilling fluid after cementing operation. The development of the new cement system focuses on optimizing the concentration of active components to provide interaction with oil-based drilling fluid, while ensuring that the rheological and mechanical properties of the cement slurry are not affected. The internal development program shows that the new system effectively reduces the hydraulic conductivity of the micro annular gap and the channeling channel with the size of 0.1 inch.

Laboratory tests are designed to measure the ability of ICS to change the oil-based drilling fluid. This measurement can be used to estimate the pressure bearing capacity during conventional stimulation operations. Preliminary results show that the additive can completely isolate the external wellbore between different well sections. An oil and gas company in the Permian Basin agreed to test the new additive in five 10000 feet horizontal wells. Cement bond logging (CBL) is used to identify the top of cement and evaluate some well sections of cementing operation from the top to hundreds of feet above the deviation making point. Review the logging results to determine if the transfer of oil-based drilling fluid can be measured. There is no doubt that there is a fluid transformation, and this result complements laboratory tests.

Most exciting of all, ICS can play a more important role in the wellbore drilled with oil-based drilling fluid. In addition to the isolation of the fracture section, there are many other reasons for the well to be isolated. For other possible applications, there are plans for additional testing.

01. Result of acoustic well cementation quality measurement

The CBL measurement results of oil wells using ICS are encouraging, and the cementing quality is greatly improved. In the first five well experiments, ICS was added to the tail mud. In one well, the additive was only applied in the horizontal section, and ICS was added in the other four wells and the whole cement section. The cement roof of all the wells is designed according to the industry standard, 500 feet above the pipe shoe.

By comparing the CBL well logs of five test wells with the datum maps, the beneficial effect of ICS is immediately shown. In laboratory tests, the forces required to displace high yield materials were measured. Therefore, CBL logging results can be interpreted more confidently to provide isolation for additives than to improve CBL response. These results will be discussed in the full text.

02. ICS concept

ICS is a stimulus responsive cement platform with simple design rules. For wells drilled with oil-based mud, poor interlayer isolation can be avoided in cementing. ICS

 contains polymer material which is dry mixed with cement before pumping. When the cement is replaced in place, the interaction between ICS and residual oil-based mud will cause obvious rheological changes, which will increase the yield value of oil-based mud in the channeling by 20 times. Maintain a pressure difference of 1000 psi every 10 feet according to the shape of the channeling. This rheological change occurs before the cement slurry reaches the ultimate compressive strength, so that the oil-based slurry channeling can withstand high pressure difference. This additive can be added to the existing slurry without any significant change in the initial target performance of the slurry and can be pumped without reducing the displacement.

In the process of increasing production, ICS is applied to improve the maximum pressure of cement sheath and channeling after reconstruction, which proves that channeling after reconstruction can bear the pressure difference between different fracture sections. This enhanced hydraulic isolation will help to avoid fractures only in the direction of low ground stress, reduce the curvature and fracture initiation pressure, and avoid the connection between well sections.

Considering the challenges of horizontal cementing, ICS is a good mitigation measure for the remaining mud. However, it cannot be regarded as a substitute for mud removal. Therefore, even if the technology is applied, the basic mud removal best process should be followed.

03. Conclusion

With the use of more field tests and other evaluation methods, including ultrasonic imaging tools, early results show that the cement system has a positive impact on cementing quality. Combined with the laboratory test, it is confirmed that the new ICS can change the oil-based mud in the channeling channel, and it is possible to improve the hydraulic sealing ability of the oil well. The effect is far better than that achieved only by removing the mud.