Novel Well Testing Procedures Prove Successful in Dakota Formation Infill Program, San Juan Basin

Abstract

Abstract Conoco implemented a novel well testing program in six infill wells to evaluate the differential pressure depletion in the Dakota formation in a portion of the San Juan Basin in Rio Arriba County, New Mexico. The field program consisted of performing pre-fracture nitrogen slug tests or pressure buildup tests. Each of the three Dakota sands were evaluated separately, and in four wells, simultaneously to estimate permeability-thickness product, skin factor, reservoir pressure, and gas in place. The novel approach allowed for all sands to be tested quickly. The infill wells were drilled on 80-acre spacing among existing 160-acre spaced Dakota wells. The Dakota formation is a series of tight, normal-pressured sands and is one of the main productive units in the San Juan Basin. The average reservoir pressure, as indicated by these tests, ranges from 2,500 psi to 2,900 psi. The original reservoir pressure was 3,200 psi. The post-fracture in-line production rates were excellent averaging between 350 to 900 Mscf/D after two months in-line. Single- and multi-well reservoir models were developed to predict the expected longterm performance from the infill wells. This paper highlights the novel pre-fracture well testing program including the methodology utilized by Conoco to meet the challenging testing needs present in the Dakota formation in San Juan Basin. The testing approach of using either nitrogen slug tests or simultaneous, individual zone, buildup tests can be used in most tight gas sands consisting of multiple sands.