Optimization of conductive fracture area is perhaps the most critical tenets of fracture stimulation. Several attempts have been implemented to improve the effective fracture area, such as hybrid fracturing, ultra-lightweight proppant (ULWP) delivery, channel fracturing, and slug fracturing. The techniques are all based on viscosity-governed proppant transport mechanisms. This paper presents a new fluid system, based on packing of soft particles, for nearly perfect proppant suspension to improve proppant transport and vertical distribution in fractures.
Proppant particles are trapped in the "void" space created by particles packing against each other, and the mechanism is completely different from that of conventional fracturing fluids. It improves effective fracture height by placing proppant across the complete productive interval under downhole conditions when properly applied. This leads to better transverse and vertical placement of proppant in the fracture and significantly increases the fractured surface area.
The fluid was tested extensively in conventional fracturing fluid protocols to confirm its feasibility because, mechanistically, it works completely different from conventional fluids. Hydration tests show that the hydration rate can be tuned to maintain the particle integrity during fracturing treatment. HPHT rheology tests show that the fluid is compatible with conventional fluid additives. Static proppant settling tests show superior proppant suspension capabilities. The fluid can be decomposed with live and encapsulated oxidizer breakers to meet treatment design requirement. The fluid can be completely cleaned up and regained proppant pack conductivity was close to unity. Interesting fluid behavior was observed during large scale slot cell testing at room temperature. The fluid was successfully applied in the Cotton Valley and it was confirmed that the novel fluid can be smoothly pumped through fracturing equipment and it also offers several operational benefits.
Criteria and considerations for successful application of such fluids to optimize proppant placement and maximize fracture conductivity are discussed. Job design is elaborated in terms of fluid mechanics and proppant transportation mechanics differences and benefits over traditional crosslinked gel systems. The execution, experiences, and subsequent well performance of treatment applications results are compared to offsets treated with a traditional crosslinked gel system.