Low-Polymer Fracturing Fluid Reduces Formation Damage

摘要

A new fracturing fluid prepared with lower amounts of guarrnpolymer can increase oil and gas production in wells byrnreducing formation damage from gelling agent residue andrnfilter cake. The low-polymer (LP) fluid consists of two primaryrncomponents: a guar gelling agent and a crosslinkingrnagent. The use of an instant or a delayed borate crosslinkerrndepends on wellhead treating-pressure limitations and piperntransit time. LP fluid is used in low-permeability formationsrnand high-permeability frac-in-pack applications with bottomholernstatic temperatures (BHST?s) up to 200oF. LP fluid canrnbe prepared with a variety of waters, including fresh water,rnKCl water, and seawater. This fluid system provides higherrnviscosities with lower gelling agent concentrations than conventionalrnborate-crosslinked fluids.rnSystem pH is important for borate-crosslinked fluids becauserna job can fail when the fluid pH is not properly adjusted andrnmaintained. The LP fluid system combines a buffer with arncrosslinker to form a single component that adjusts fluid pHrnto an optimum level for crosslinking. Other crosslinked fluidrnsystems usually require a third component to adjust systemrnpH. The single-component buffer/crosslinker additive in LPrnfluid makes field applications more simple and reliable.rnIn general, rheology, fracture conductivity, fluid efficiency,rnand proppant transport data for the LP fluid system closelyrncompare to properties of conventional borate-crosslinkedrnfluids containing polymer concentrations that are 10 to 15rnlbm/Mgal higher. Since proppant-pack cleanup after fracturingrnis an important component of production, the lower gel rnloading is credited with the increased production seen in wellsrnin which the LP fluid system is used. LP fluids containing 15rnto 25 lbm of gelling agent/Mgal can be used to fracturestimulaternwells in areas that previously used conventionalrnborate-crosslinked fluids containing 25 to 40 lbm of gellingrnagent/Mgal. Lower amounts of gelling agent provide betterrnand more complete fluid breaks in fractures, resulting in fasterrnfluid recovery and higher regained proppant-pack conductivity.rnDecreasing the amount of gel used in fracturing fluid alsornprovides significant upfront treatment cost savings.