Engineering Solid Particulate Diverter to Control Fracture Complexity: Experimental Study

Abstract

Enhancing complexity of the created fracture geometry is the primary challenge for hydraulic fracturing treatment design in shale formations because of their stress anisotropy. Therefore, near-wellbore diversion is required to evenly stimulate all perforated clusters while far-field diversion inside the created fracture induces additional branch fracturing by overcoming the stresses holding the natural fractures closed. Solid particles with different shapes and sizes are widely used as diverting agents during fracture treatments. The recommended particles should temporarily bridge inside the fracture to create a low- permeability pack that increases the pressure within the fracture and enables redirection of next-stage fluid to understimulated intervals. The objective of this study is to experimentally investigate and optimize parameters affecting the selection of solid particles as diversion agents such as material chemistry, particle size, particle shape, particle size distribution, particle loading, carrier fluid type, and carrier fluid viscosity. Three tests were performed in this study: Bridging tests to determine the optimized particle size and loading as function of fracture width (0.04 to 0.2 in.); pack permeability tests to optimize the particle size distribution and shape needed to minimize fracture conductivity and build the needed pressure; and dynamic dissolution tests to determine the time need to completely dissolve the particles as function of temperature, rate, particle size, and produced fluid. The results of this paper can help in understanding the diversion parameters required to effectively enhance the complexity of the fracturing geometry. For far-field diversion applications (targeting fracture widths of 0.04 to 0.08 in.), larger particles are not required, as the fracture width is small. However, very tight particle pack permeability is needed. For near-wellbore and perforation diversion (targeting fracture widths of 0.2 in. and higher), only larger particles can bridge the wider fractures. Therefore, a wider (in this case tri-modal) particle size distribution is required: coarse particles to bridge the fracture along with a bi-modal distribution of medium and small particles to minimize the particle pack permeability and achieve the diversion. A diverter pack with bi-modal size distribution and higher concentration of small particles reduces particle pack permeability more than a tri-modal size distribution with more medium-size particles. Diverter A and B tested in this study were able to bridge inside the fracture, reducing its conductivity by converting the open width into a porous medium with a tight permeability for both applications: far-field and near-wellbore. Diverter A (NW) is more efficient and effective than commodity benzoic acid flakes for a simulated near-wellbore application with a fracture width of 0.2 in. The diverter pack dissolved more slowly in slickwater fluid than in DI water, probably more due to the slickwater's polymer content than its minimal increase in viscosity.

Review of Shale Oil and Gas Refracturing: Techniques and Field Applications

“…The shale gas wells in the Fuling shale gas reservoir have exhibited a significant decline in production over time, necessitating the need for refracturing to enhance the recovery rate of the gas field [46]. In terms of temporary plugging and refracturing technology, Sinopec has conducted on-site trials at several wells in the Fuling shale gas reservoir, demonstrating the feasibility of this technology.…”

Experimental study of the temporary plugging pattern of perforations by multi-particle size composites

“…In contrast, there are relatively few experimental studies on the temporary plugging of perforations, in which there are large discrepancies between the simulation of perforations and actual perforations [6]. The widely adopted method to simulate the perforation is to make a circular hole in the center of the metal plate and consider this hole as the perforation [15][16]. Based on this, a metal simulated perforation with a small core column size and a circular platform-like channel inside the metal to simulate a wedgeshaped perforation shape [17].…”

An Artificial Intelligence-Based Model for Performance Prediction of Acid Fracturing in Naturally Fractured Reservoirs

“…Acid is usually injected in stages separated by nonreactive (i.e., pad) fluid injection. These nonreactive stages could also contain diverters to reduce fluid loss and plug natural fractures. , …”

“…These nonreactive stages could also contain diverters to reduce fluid loss and plug natural fractures. 4,5 Performance prediction of acid fracturing operations is necessary to optimize the design. 2 Conventionally, computational models were developed to estimate the acid penetration distance and fracture conductivity.…”