High Strength, Ultra-Lightweight Proppant Lends New Dimensions to Hydraulic Fracturing Applications (2003)

High Strength, Ultra-Lightweight Proppant Lends New Dimensions to Hydraulic Fracturing Applications Allan R. Rickards; Allan R. Rickards BJ Services Search for other works by this author on: This Site Google Scholar Harold D. Brannon; Harold D. Brannon BJ Services Search for other works by this author on: This Site Google Scholar William D. Wood; William D. Wood BJ Services Search for other works by this author on: This Site Google Scholar Christopher J. Stephenson Christopher J. Stephenson BJ Services Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 2003. Paper Number: SPE-84308-MS https://doi.org/10.2118/84308-MS Published: October 05 2003 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Rickards, Allan R., Brannon, Harold D., Wood, William D., and Christopher J. Stephenson. "High Strength, Ultra-Lightweight Proppant Lends New Dimensions to Hydraulic Fracturing Applications." Paper presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 2003. doi: https://doi.org/10.2118/84308-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractSince the earliest fracturing treatments over 50 years ago, many different materials have been used including sand, glass beads, walnut hulls, and metal shot. Today's commonly used proppants include various sands, resin-coated sands, intermediate strength ceramics, and sintered bauxite, each employed for their ability to cost effectively withstand the respective reservoir closure stress environment. As the relative strength of the various materials increases, so too have the respective particle densities, ranging from 2.65 g/cc for sands to 3.4 g/cc for the sintered bauxite. Unfortunately, increasing particle density leads directly to increasing degree of difficulty with proppant transport and a reduced propped fracture volume for equal amounts of the respective proppant, reducing fracture conductivity. Intuitively, one expects a lesser density proppant would be easier to transport, allowing for reduced demands on the fracturing fluids, and if it had sufficient strength, would provide increased width, hence, enhanced fracture conductivity.Previous efforts undertaken to employ lower density materials as proppant have generally resulted in failure due to insufficient strength to maintain fracture conductivity at even the lowest of closure stresses (1,000 psi). Recent research on material properties has at last led to the development of an ultra-lightweight material with particle strength more than sufficient for most hydraulic fracturing applications. The current ultra-lightweight proppants have apparent specific gravity's of 1.25 and 1.75 g/cc. Laboratory tests will demonstrate exceptional fracture conductivity at stresses to 8,000 psi. This paper will present data illustrating the performance of the new ultra-lightweight proppant over a broad range of conditions and a discussion of relative performance in field applications.IntroductionUltra-lightweight proppants have been a subject of research efforts for at least a decade. Generally speaking, the stronger a proppant, the greater the density. As density increases, so too does the difficulty of placing that particle evenly throughout the created fracture geometry. Excessive settling can often lead to bridging of the proppant in the formation before the desired stimulation is achieved. The lower particle density reduces the fluid velocity required to maintain proppant transport within the fracture, which, in turn, provides for a greater amount of the created fracture area to be propped. Alternatively, reduced density proppants could be employed to reduce fracturing fluid complexity and minimize proppant pack damage.Two different avenues of ULW particle development research pursued in this area are presented. The first is a porous ceramic that uses novel resin technology to coat the outside of the particle without invading the porosity to effectively encapsulate the air within the porosity of the particle. Encapsulation of the air provides preservation of the ultra-lightweight character of the particles once placed in the transport fluid. Additionally, the resin coating significantly increases the strength and crush resistance of the ultra-lightweight ceramic particle. In the case of natural sands the resin coat protects the particle from crushing, helps resist embedment, and prevents the liberation of fines.The second avenue of research was directed towards an even lighter particle which may be described as a resin-impregnated and then, coated, cellulosic particle. The cellulosic substrate is sized, ground walnut hull. The low specific gravity of this particle allows near neutrally buoyancy behavior in flowing streams of slickwater type fluid. The application benefits of the ULW proppant are further enhanced beyond those discussed above. Resin impregnation and coating provide significantly enhanced strength beyond that afforded by the unaltered walnut hulls alone.Statement of Theory and DefinitionsThe ULW-1.75 is a porous ceramic particle with the roundness and sphericity common to ceramic proppants. The porosity averages 50%, yielding a bulk density of 1.10 to 1.15g/cm3. Resin chemistry and processing technology have been developed to coat the particles, protecting the porosity from fluid invasion. If the resin coating or transport fluids were to significantly penetrate the porosity of the particle, the density increases accordingly, and the particle no longer has the same lightweight properties. The resin coat also adds strength and substantially enhances the proppant pack permeability at elevated stress. A comparison of the permeability versus closure stress of 1 lb/sqft of ULW-1.75 compared to Econoprop and Ottawa sand is shown in Figure 1. Keywords: fracturing materials, upstream oil & gas, bulk density, conductivity, fracturing fluid, hydraulic fracturing, slickwater, strength, ultra-lightweight proppant, shear rate Subjects: Hydraulic Fracturing, Fracturing materials (fluids, proppant) This content is only available via PDF. 2003. Society of Petroleum Engineers You can access this article if you purchase or spend a download.