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AbstractThis paper reviews the fracture stimulation improvement achieved over the recent three years with extensive field redevelopment and workover against the backdrop of fracture development of the Western 31S (W31S) Stevens Oil Zone in the central California Elk Hills field since 1998.The W31S is one of the major Stevens reservoirs within the huge 31S anticline structure. It has low to moderate permeability distribution and severe layering throughout the pay interval. From experience, significant stimulation is often required to overcome near-wellbore formation damage and generate favorable economics to sustain a redevelopment drilling program. Perforation, matrix acidizing and fracture stimulation have been performed on cased hole completions with varying degrees of success.Hydraulic fracture stimulation introduced in the W31S much later, proved to be very successful in improving well productivity but has enormous operational and production problems associated with it that required process improvement. Such problems ranged from in-situ stress variations that may lead to pre-mature screen-out, proppant diversion with cement integrity issues common with older wellbores, proppant flow back problems, effective vertical coverage of the target pay intervals, gel residue and the consequent damage to fracture conductivity. While acid treatments were sometimes used to remove the created damage on a few of the W31S wells, several of the wells have serious limitations on well performance that would be difficult and costly to remove.Significant gains in production have been observed following successful fracture treatment optimization. The use of a unique small-chain polymer, high performance viscoelastic fracturing fluid (HPF) lead to higher per well productivity and minimized post-frac production problems compared to past jobs with conventional fracture treatment containing borate crosslinked guar polymer and encapsulated oxidizing breakers.