A major challenge that is being occasionally faced during the well construction phase is to cement the formations holding narrow pressure margins between the pore and fracture gradients without inducing losses. Losses can commonly occur in these cases, compromising the integrity of the cement barrier. Designed slurry densities generally lead to high equivalent circulating density (ECD) levels during the cementing operations. This condition, combined with mud weights conventionally designed to be above pore pressure, usually results in downhole pressures which approach or exceed the fracture limit. Commonly, operators implement strategies to mitigate losses during the cementing phase, however, in most cases the losses are unavoidable using a conventional cementing approach. Managed pressure cementing (MPC) is an important technique for primary cementing operations in wells with such narrow pressure margins. This paper presents the design considerations, methodology and results of a land well where high-pressure influx was encountered while drilling an 8-3/8-in hole across a water-bearing formation. Narrow pressure gradient persuaded to utilize managed pressure drilling (MPD) to continue the drilling. The well was drilled to the target depth using 138-lbm/ft3 oil-based drilling fluid while maintaining the ECD from 146.5 to 149.5 lbm/ft3. Careful attention was paid to estimate the bottom hole circulating temperature, using the temperature modeling simulator. A 150-lbm/ft3 slurry was designed to keep the ECD intact. The slurry was batch-mixed to ensure the homogeneity of the final slurry mixture. A special spacer system was designed to reduce the losses while cementing. Additionally, the spacer was loaded with optimum amounts of surfactant package to serve as an aid to remove the mud and to water-wet the formation and pipe for better cement bonding. The centralizers placement plan was optimized, and additionally the liner was rotated during the cement job to achieve the required displacement efficiency yet staying within the torque and drag (T&D) limits. The cement treatment was performed as designed and met all zonal isolation objectives. The managed pressure cementing (MPC) system provides safe isolation of problematic zones in cost effective manner even in challenging narrow pressure window scenarios. The system provides precise control of the pressure and flow during and after the cement job. Constant pressure can be achieved at weak zones, preventing losses to the formation. This case study presents an overview of the engineering process used to plan and design the MPC operations and the results obtained. This paper reviews a successful MPC operation and presents findings and lessons learnt. After the successful results on this job and subsequent operations, this technique is now being adopted to optimize cementing, where losses during cementing operations in the past had forced to modify the well construction.
A major challenge that is being occasionally faced during the well's lifecycle is the pressure buildup between the cemented casing annuli, also known as sustained casing pressure (SCP). Compromise of cement sheath integrity is one of the primary reasons for such a pressure buildup. This challenge prompted to develop such an isolation material that should enhance the mechanical properties of cement. The resin-cement blend system can be regarded as a novel technology to assure long term zonal isolation. This paper presents the lab testing and application of the resin-cement system, where potential high-pressure influx was expected across a water-bearing formation. The resin-cement system was designed to be placed as a tail slurry to provide enhanced mechanical properties in comparison to a conventional slurry. The combined mixture of resin and cement slurry provided all the necessary properties of the desired product. The slurry was batch-mixed to ensure the homogeneity of resin-cement slurry mixture. The cement treatment was performed as designed and met all zonal isolation objectives. Engineered solutions ultimately deliver the optimal asset value of the reservoir. During the last few decades, several laboratory investigations and field studies have been conducted to find solutions to the problem of SCP, which appears after primary or remedial cement jobs. Almost all these studies unanimously conclude that the conventional cement does not always endure the mechanical stresses imposed by the wellbore conditions and it often falls short in providing long term isolation beyond the production life of the well. When the resin is introduced into a cement slurry, it forms a dense, highly cross-linked matrix. The extent of the cross-linking reaction is governed primarily by volume, temperature, and time. The distribution of resin throughout the slurry provides a shock-absorbing tendency to the particulates of the cement. This feature increases the ductility and the resilience to withstand stress from load-inducing events throughout the life of the well. Resin-cement's increased compressive strength, ductility, and enhanced shear bond strength help to provide a dependable barrier that would help prevent future sustained casing pressure (SCP).
A significant challenge occasionally faced during the well's lifecycle is the pressure buildup between the cemented annuli, also known as sustained casing pressure (SCP). The presence of SCP indicates a path of flow of formation fluids to the surface. Compromise of cement sheath integrity is one of the primary reasons for such a pressure buildup. This challenge prompted the development of such an isolation material that should enhance the mechanical properties of cement to prevent the SCP. In parallel, another isolation material was required to remediate the wells suffering from SCP. After some research, a specialized resin system was developed that could be deployed to prevent and eliminate the SCP in the situations mentioned above. This paper presents the lab testing and application of the innovative resin system. This system can be used as a standalone product and blended with cement, depending upon the nature of the application and zonal isolation objective. While using the resin as a standalone product, its solids-free nature and low yield point enable it to flow freely into micron-sized leaks or channels. Pure resin is mainly used for remedial applications. When the resin is added to the cement during primary cementing operations, it forms a dense and highly cross-linked matrix with improved mechanical properties that helps to provide a dependable barrier to maintain long-term zonal isolation. Engineered solutions ultimately deliver the optimal asset value of the reservoir. During the last few decades, several laboratory investigations and field studies have been conducted to find answers to the problem of SCP, which appears after primary or remedial cement jobs. Almost all these studies unanimously conclude that conventional cement does not always endure the mechanical stresses imposed by the wellbore conditions, and it often falls short in providing permanent isolation beyond the well's production life. This paper illustrates two case studies to validate this. The first case study is related to primary cementing, where the resin-cement blend was successfully utilized to prevent the expected high-pressure influx across a water-bearing formation. The resin-cement system was designed to be placed as a tail slurry to provide enhanced mechanical properties compared to a conventional slurry. The combined mixture of resin and cement slurry provided the desired product's necessary properties. The cement treatment was performed as designed and met all zonal isolation objectives. The second case study relates to remedial cementing, where the resin system was utilized to remediate the three annuli on an offshore oil well. Reliable and effective annular barriers are critical to well management for safety and performance. Conventional Cement slurries have been the industry's typical means of creating these barriers. However, the cement alone is inadequate to meet the industry needs; hence, combined solutions deliver improved well integrity.
This paper discusses the designing and field application of a polymer resin-based cement system that enhances the final cement properties in terms of compressive strength and cement bond to the casing along-with minimizing the occurrence of casing-to-casing annulus (CCA) pressure during the life cycle of the well. Several experimental studies were applied to this polymer resin-based cement system including rheology, thickening time test, free fluid test, compressive strength test, etc. The results showed that the polymer resin-based cement has improved compressive strength, ductility, and enhanced shear bond strength. Which, as a result, helps to provide a dependable barrier that would help to prevent future sustained casing pressure (SCP). Besides, the cement slurry was designed with a controlled and engineered rheology. This was done by controlling the amount of the resin and cross-linker into the cement slurry in order to achieve the target density as well as to avoid a sudden increase in the final slurry viscosity that could result in mixing difficulties at the field. Moreover, the field deployment of this system on a 13 3/8-in casing second stage tail slurry has been discussed.
Sustained casing pressure (SCP) has been a major challenge in terms of well integrity management, all around the world. Cement is the main element that provides isolation and protection for the well. The cause for pressure build-up in most cases is a compromise of cement sheath integrity that allows fluids to migrate through micro-channels from the formation to the surface. This paper presents lab work and field application that support the efficiency and reliability of an innovative resin system in enhancing the wellbore integrity. This paper presents the development for potential wellbore isolation issues for casings utilizing surface treatments. Due to the solids-free nature and enhanced bonding characteristics, the resin system was utilized. The preparation for this job was unique due to the extremely limited injectivity rate, it was not possible to perform the job by utilizing the conventional cementing equipment, hence a specialized high-pressure pump with-having a very low pump rate capability was utilized for this unique pumping methodology. Multiple treatments were mixed and pumped as planned to achieve the desired set of results. Lab testing included thickening time tests, rheology, contamination, and compatibility testing. Globally, conventional cement systems are often ineffective in potential remedial operations because of the high concentration of solids present within these systems. Therefore, the resin system is the best choice for this kind of potential remediation. The carefully timed setting ensured the optimum penetration and placement before the resin cured up and ensured the potential channel got permanently sealed. The proposed solution in this paper can add great value to restore the well's integrity and to save the rig's operational cost globally. The resin system is evolving as an emerging solution within the industry, replacing conventional cement in many potential crucial remedial applications. This paper highlights the necessary laboratory testing, field execution procedures, and treatment evaluation methods so that this technology can be a critical resource for such potential remedial operations in the future.
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