Compositional Simulation of the Coyanosa Wolfcamp Field Gas Cycling Operation

Abstract

ABSTRACT The Coyanosa Wolfcamp Field, located in Pecos County, Texas was discovered in September 1962. The reservoir rock is comprised of poorly sorted, coarse-grained heterogeneous conglomerates with thinly interbedding shaly limestones. The dew point pressure of the Gas Unit reservoir ( representing about 80% of the Coyanosa Wolfcamp Field pore volume ) was 6,179 psia at a reservoir temperature of 175°F. The initial reservoir pressure was 6,700 psia. Mobil initiated a gas cycling operation in August 1964. The condensate yield has declined steadily during the lean gas cycling operation. A compositional simulation study was undertaken to simulate complex mass transfer and composition changes. The study's objectives were to estimate the remaining condensate reserves and to determine an efficient depletion scheme including an optimum reservoir blowdown timing. After matching the past 23 years of the product-ion history, the model was then used to predict future performance under the various operating scenarios.The sensitivity of liquid recovery to pressure, rate and degree of cycling was investigated. Depletion plans such as added compression, partial cycling and immediate blowdown were evaluated to devise an optimal operation plan.