Nanoparticle-Based Fluids Reverse Long-Term Hydrocarbon Decline

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 3848516, “Tailored Metal Oxide Nanoparticles-Based Fluids in Acid Restimulation Treatments Reverse Long-Term Hydrocarbon Decline: A Pilot Study in Wolfcamp A Formation,” by Panagiotis Dalamarinis, SPE, DG Petro Oil and Gas, and Amr Radwan and Raja Ramanathan, TenEx Technologies, et al. The paper has not been peer reviewed. Multifractured horizontal wells suffer from high hydrocarbon decline and water cuts after initial flowback. This behavior is in part because of near- and far-field-fracture conductivity damage. Refracturing operations (acid or proppant) can mitigate these problems, yielding a good cleanout performance and stable oil-recovery trends. The complete paper details a successful pilot to improve long-term well performance using acid stimulation aided by a pioneering tailored metal oxide (TMO) nanoparticle-based fluids in the Wolfcamp A formation. The reason for replacing normal surfactants with the TMO nanofluid was its ability to create bonds between the fracture phase and rock matrix, overcome the problems normal surfactants demonstrate, and provide long-term production maintenance. The nanofluid is made of proprietary blends of metal oxide nanoparticles and other additives to improve stability and compatibility under harsh reservoir conditions. The nanofluid was engineered to be effective under a wide range of lithologies, salinities, crude oils, temperatures, and pH changes. The nanofluid is a nontoxic, nonhazardous, water-based fluid containing one or multiple types of metal oxide nanoparticles with stabilizing chemistry. The size of the nanoparticles can be as low as 3 nm. The nanofluid works by a mechanism called structural disjoining pressure, or “uplift pressure.” The nanoparticles form a wedge underneath the organic matter and allow it to disconnect from the surface against different crude-oil types that may overcome normal surfactant limitations by replacing conventional chemical-based solutions. The TMO nanofluid has shown a trend of alleviating the decline rate in treated wells that is believed to be linked to the long-term wettability alteration mechanism. The effectiveness of the treatment improves when the nanofluids can be tailored to specific crude oils and rock mineralogy. Two groups of wells were used in this study, one in Reeves County (three wells) and one in Culberson County (four wells). Each group of wells had different reservoir and production characteristics. For each of the wells, water and oil samples were collected, analyzed, and, based on this data, nanofluids were used in one well of each group instead of normal surfactants. The artificial lift systems used after the acid restimulation of all wells presented in this study were electrical submersible pumps (ESPs). After the initial flowback (approximately 2 weeks), when the targeted production rates for each well were achieved, the ESPs were operated with a schedule that allowed similar drawdowns for all wells of approximately 5 psi/day. This approach was selected to provide better relevance to the production performance and evaluation of the wells but also to manage reservoir drawdown and offset-well interference.