Abstract

Early fracture treatments in the AWP (Olmos) field utilized over 1,000,000 lbs. of 20/40 mesh Ottawa sand. While production results were good, mechanical problems Md production results were good, mechanical problems Md economic factors necessitated alternative treatments. Smaller volume schedules were tried, but the resulting production lagged the larger jobs. Recently, treatments designed with resin coated sand (RCS) improved well performance. The stronger RCS maintains better conductivity at lower proppant concentrations with resultant good production response at a lower total cost. As an additional benefit, the curable RCS bonds together to eliminate proppant flowback.

Introduction

The Olmos formation produces from 9,800 feet average depth in the AWP field. Historically, massive hydraulic fracture (MHF) stimulations averaged over 1,000,000 pounds of 20/40 mesh Ottawa sand Md were designed for an average proppant pack of 4 lbs./sq.ft. using a Geertsma-DeKLerk proppant pack of 4 lbs./sq.ft. using a Geertsma-DeKLerk fracture simulation model. The large volume treatments compensated for the loss of conductivity from crushing, embedment, Md plugging. However, a drawback of these treatments was the flowback of proppant into the wellbore. In 1986, falling oil prices necessitated smaller proppant schedules. Fracture height control treatments preceded 702,000 lb 20/40 mesh Ottawa sand schedules. Initial production rates were 75-130 BOPD, but most wells production rates were 75-130 BOPD, but most wells experienced severe decline rates and required refracture treatments. A continuing problem during production was the wellbore inflow of proppant. This created additional workover expense during a time of budgetary constraint. Next, a proppant schedule applying a combination of precured Md curable resin coated sands was designed to precured Md curable resin coated sands was designed to minimize crushing, reduce embedment, and stop proppant flowback. Since crushing was minimized, proppant pack concentrations were reduced to M average of 3 lbs./sq.ft. This reduction aided in controlling fracture height and job cost. In excess of forty treatments have been pumped with a design averaging 400,000 pounds of RCS. The higher cost of RCS was offset by treatment size reductions. The wells maintain better production than comparable offsets, with no proppant flowback.

FIELD HISTORY

The AWP (Olmos) field lies in McMullen County, Texas about five miles east of Tilden. The productive reservoir extends approximately four miles east-west and seven miles north-south (Figure 1). Production comes from the very tight Olmos sandstone, an upper cretaceous system, at about 9,800 feet in depth. Stratigraphy controls the oil and gas accumulation with structure influencing production very little. In general, the reservoir dips to the southeast at about 150 feet per mile and is interrupted by local faulting. per mile and is interrupted by local faulting. The Olmos is a soft fine grained sandstone containing as much as 25% clay. The productive reservoir rock has a porosity exceeding 13%. Permeability is 0.1 millidarcy or less, porosity exceeding 13%. Permeability is 0.1 millidarcy or less, and water production is insignificant. Commercial production requires a hydraulic fracture treatment.

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