Identifying and Isolating Water Production in a Highly Saline Environment Through Well Intervention Techniques

Abstract

Abstract The global energy industry is going through a paradigm shift from aggressive exploration to sustainable production enhancement in order to maximize recovery from brownfields and play their part in minimizing carbon emissions. For this, active reservoir surveillance will remain at the forefront for informed decision making. Production logging has played a crucial role in production optimization to boost recovery efficiency in producing wells. Water production hinders the productivity of wells because of its higher gravity, causing a downhill impact on the recoverable hydrocarbons. Moreover, if water salinity is high (>250,000 ppm), it brings additional challenges of handling highly saline water at the surface for treatment and disposal. This work is the culmination of technical and operational brilliance that helped to not only identify water production of Well XX, located in a structurally complex field with liquid loading issues, but also to isolate the water-producing zone downhole in a highly challenging saline environment where cement settling is a big challenge. The field under consideration has diverse fluid characterization, with transition from retrograde condensate to black oils across the field. Most wells are completed commingled in two main reservoirs; both are sandstone in a highly faulted area. In addition to geological complexities, water dynamics are also variable across the field, with some producing water from a shallower reservoir while other wells from the deeper one. The subject Well XX was completed in open hole through a fracture string and was producing commingled from the two reservoirs with high water/gas ratio (WGR) of 72 bbl/MMscf, urging the need for water conformance. Therefore, as a first, extensive planning was done prior to the production logging job, to ensure water entries are identified accurately through a fit-for-purpose production logging suite. Second, vigilant real-time monitoring was performed to optimize surveillance to ensure good-quality data. This was followed by setting a mechanical plugback tool (MPBT) to cease crossflow between both reservoirs. Third, based on laboratory experiments, it was identified that highly saline and acidic water reduces the compressive strength of cement and reduces thickening time, which makes cement plugs highly unreliable in such an environment. This highly saline (>250,000 ppm) and acidic water issue was addressed by replacing the environment with 5% potassium chloride (KCl) brine and using 30% excess cement with coiled tubing. Moreover, acid-soluble cement was used to protect the water-free reservoir such that if cement is lost, acid can help to dissolve it. With comprehensive diagnostics and optimized operations, water production was curtailed, resulting in improved wellbore dynamics that enhanced the hydrocarbon production from the well. This helped the operator to save operational costs of water handling at the surface and improve hydrocarbon recovery from the well. To facilitate the proper setting of cement for water conformance in a highly saline downhole environment, smart operational optimization was performed by replacing incompatible, highly saline formation water with suitable fluid before dumping the cement, thereby ensuring proper isolation within the wellbore.