A Case Study of the Evaluations Completion' and Testing of a Devonian Shale Gas Well

Abstract

Summary This paper summarizes the operational procedures, geochemical analyses, well-log-interpretation techniques, perforation selection methodology, production-log interpretation, well-test analysis, and stimulation evaluation for a Devonian shale gas well in Pike County, KY. Contractors collected well-log, core, geochemical, and well-test data in addition to those which the operator would have routinely collected on this well. The purpose of this paper is to discuss the data collected on the well, to present the data analyses and to demonstrate how the various analyses are being integrated to form a better overall understanding of Devonian shale gas reservoirs. Introduction This paper summarizes the work l performed on a Devonian shale gas well in Pike County, KY, called Well Pike 31. This well is in the Big Sandy gas field, which is the largest Devonian shale gas field in the Appalachian basin. Well Pike 31 was part of a multiwell research program red by the Gas Re search Inst. (GRI). Fig. 1 illustrates the location of Well Pike 31 relative to the other wells studied in this program. GRI sponsored this research program in the Appalachian basin as part of its continuing research efforts in gas supply. The overall objective of this field-oriented program was to develop a better understanding of the relationships between gas production in the Devonian shale and factor that control and influence gas production. Specifically, the objectives of the research were to identify zones of gas entry from the Devonian shale, to determine the geologic and reservoir properties of those zones, and to identify, where possible, the variations in well productivity resulting from differing stimulation and completion practices as opposed to variations in geology. This research program was conducted in cooperation with operators in the Appalachian basin. Thirty-five cooperative wells were studied as part of this program. GRI contractors collected well-log core, and well test data in addition to those which the operator would have routinely collected on these wells. For some wells an air dryer was used to drill through the Devonian shale sequence. In most wells, a detailed suite of openhole geophysical logs, a mud log, a temperature log, and a suite of cased-hole production logs were run. The borehole television camera was used to identify fluid entries and fracturing. Wellsite geochemical analyses were performed on nine study wells. Prestimulation flow and pressure-buildup test were conducted on several wells. Poststimulation flow and pressure-buildup tests were conducted on more than half the study wells. In each of these cooperative wells, the operator retained control of daily well operations. Decisions regarding where wells should, be completed, how they should be stimulated, and how they show be tested were made by the operator. GRI contractors provided recommendations concerning the completion interval, the stimulation type and size, and the well-testing guidelines only when requested by the operator.