The focus of the international oilfield industry is clearly increasing toward the development of unconventional plays worldwide, and this increased focus is evident in the development of local shale formations in the Neuquén basin. The emerging unconventional market in western Argentina constitutes most of the drilling operations in the region. Well integrity is a key requirement for these projects that demand distinctive completions through massive hydraulic fracturing. Existing conditions within the field add major challenges to the overall well construction process, considering the high pore pressure and the ultranarrow operative window (i.e., tight pore-fracture margin) present along the production section. These conditions increase the demand for dynamic pressure management techniques. Shale-targeted wells were cemented overbalanced at first; however, the failure rate was high, leading to annular pressure buildup (APB) problems requiring costly remediation. Some wells could not even reach total depth (TD) and were temporarily abandoned. Presently, most of the unconventional wells drilled in the area are cemented using a managed pressure cementing (MPC) technique, which has considerably improved the success rate. After defining critical anchor points, an engineering design methodology is proposed to adjust a dynamic backpressure profile to effectively control the formers. Considering the APB rate as the evaluation criteria in place, this engineering approach has made cement placement in local unconventional wells more effective than ever before, increasing the success rate from approximately 67% in 2013 to nearly 95% in Q1-2015.

The increasing energy demand has led shale unconventional reservoirs to become a focal point for operators worldwide. Over the past decades, several technological advances were conveyed to drilling and completing horizontal geometry wells in which massive hydraulic fracture treatments are deployed to improve production of these reservoirs. Argentina has one of the largest shale-stored hydrocarbon reserves in the world and has become one of the leading countries in the exploration, appraisal, and development of unconventional reservoirs. The number of horizontal shale wells drilled in the country increased over the past decade, generating the need to find solutions to cement horizontal laterals and achieve the required zonal isolation for the normal completion and production of these wells, preserving well integrity. Based on the difficulties encountered to cement these horizontal wells, such as channeling and differential fluid velocities, among others, the need to implement casing rotation while cementing was considered. This mechanical method has remained locally as one of the least accepted solutions because of the fear that the high torques during the operations would cause casing failures. In a recent unconventional campaign, casing rotation was applied during well conditioning and along the cementing operation. A sensitivity study to rotational speed was performed, and the cementing design was optimized with a new 3D annular displacement simulator (3D-ADS) that predicts annular flow in complex geometries, accounting for pipe movement. The well was cemented successfully, obtaining congruent results from comparing bond logs and fluid placement simulations. This study defines some of the factors contributing to a successful cementing job in a horizontal geometry, the aspects to be analyzed from the cementing perspective when rotating casing to aid in mud displacement, and the evaluation of the wells cemented under these circumstances compared to the simulated results predicted during the design phase of the well.

This work describes some technologies that have been applied in several wells in southern Chile to improve zonal isolation between different reservoir sections and minimize unwanted water production; an excellent cement bond is a key requirement. There are several challenges to the success of a cement job: the presence of gas-bearing zones in the wellbore that can destabilize the cement system causing it to fail, the presence of formations sensitive to filtrates from the drilling fluids and cement, and the climatic conditions in southern Chile during winter. In addition to these factors, the well needs to be cemented without generating any formation damage that could impair the well productivity. The paper describes a multiwell solution consisting in the utilization of a solid gas migration (SGM) technology that, combined with a high-performance cement system and an engineered train of preflushes, allows achieving the ultimate goal of obtaining excellent cement quality and minimum formation damage. The SGM technology is suitable for use at very low ambient temperatures, and it provides effective gas-tight properties while minimizing the fluid loss of the slurry. The solution has proved to be extremely effective in controlling gas migration, even under extreme situations where neighboring wells presented serious sustained casing pressure (SCP) problems. The novel SGM technology utilized also allows improvements in logistics by reducing the preparation time and equipment requirements for the job, thus providing a more sustainable well construction process. In addition, the cold-tolerant additives used provide significant value when preventing nonproductive time at the wellsite and, at the same time, eliminating the disposal of mix water containing liquid additives degraded because of the freezing cycles. To date, more than 20 wells, with gas severity ranging from moderate to high, have been successfully cemented using this approach. The paper provides details of the engineering approach and examples, including cement logs.