Gas wells with high porosity and a low productivity index have mechanical and petrophysical properties that require fracture development to improve productivity. Fundamental solutions through treatment design have a lower impact than the characteristics of the reservoir and rock properties. Problems related to controlled fracture geometry, excessive fluid leakoff, proppant settling, proppant flowback, and near-wellbore and far-field diversion do not have promising solutions. Utilization of degradable chemistry, especially with ability of simulating the performance with advanced numerical models, has promising and underutilized potential for fracturing, stimulation, and production optimization.
Numerous versions of fibers and particulates with different particle distributions were developed with polylactic acid (PLA) chemistry by altering properties and morphologies for applicability over a wide range of 140 to 350°F. Techniques such as dynamic fluid loss, plugging, degradation, and core-flow testing and scanning electron microscopy were used to characterize, evaluate, and qualify the product for a tailored solution. Nine challenging cases were studied using rigorous integration of laboratory experimentation and state-of the art high-fidelity, high-resolution, multiphysics, multimaterial fracture modeling in the design and evaluation phases. Degradation acceleration was studied and optimized using various chemical media to avoid long well shut-in times and rock pore throat and surface line plugging.
The following cases and resolutions are detailed in the paper: (1) In a high-leakoff formation with fracturing fluid efficiency (FE) of 4.7%, the 150-µm version of the PLA powder was used to increase the FE to 27%. This enabled successful proppant placement and reduced formation damage. (2) In a well with a parted liner, the target perforation interval was inaccessible. We perforated above the deformed region to access the target net pay from above. Due to the high Young's modulus at perforations, there is a huge risk of proppant settling and loss of wellbore-fracture connection. Fiber-laden slurry allowed saving this challenging intervention well with commercial post-fracturing production. (3) A strategic proppant and fibers composite mixture was used to create an artificial stress barrier. Height growth control allowed successfully avoiding contact with the water-gas contact 70 ft away from the bottom perforation. The production showed no formation water. The concept can be used for fracture geometry control overall to reduce fracture-driven interactions. (4) Fibers were used to increase the CO2 foam stability and decrease proppant settling twofold, enabling treatment placement by decreasing proppant friction by 62% with no indications of the near-wellbore bridging observed in CO2 foam without fibers. (5) Near-wellbore diverters were used to mitigate interstage communication in openhole multistage acid fracturing with packers. The technique is extendible to controlling losses in coiled tubing interventions and plugging other completion elements such as flow control valves. (6) Engineered multimodal near-wellbore diverters were used to enhance stimulation and operational efficiency ~threefold and reduce 58% of the stages required to have effective reservoir contact. (7) Far-field diversion was achieved successfully with fiber-laden viscous acids for low-, mid-, and high-temperature carbonates. (8) Proppant flowback control was achieved with use of fibers. (9) Fibers were used in cleaning/scrubbing applications.
