Abstract

The Hydraulic Fracture Test Site in Reagan County, Texas contains a valuable dataset to correlate the occurrence, position and frequency of microseismic events in relation to physical observations of hydraulic fractures taken from a low-angle whole core acquired immediately adjacent and subsequent to a modern hydraulically fractured horizontal well within the Upper & Middle Wolfcamp formations. Microseismic event density maps visualized through time locate concentrations of microseismic activity in relation to independently documented hydraulic and naturally occurring fractures. Microseismic activity observed over the duration of a single completion stage at the closest proximity to the cored interval demonstrates conformity and correlation with the presence of hydraulic fractures. Changes in microseismic signature are also correlated with changes in pump rates and pressures throughout treatment. A positive correlation was found between the high certainty hydraulic fractures observed in the core and areas of highest microseismic density in the stage of the neighboring horizontal nearest to the Upper Wolfcamp cored interval of the slant well, demonstrating that microseismic density can be a reliable indicator of hydraulic fracture density and complexity around the stimulated well. Given caveats often cited with microseismic acquisition, processing and interpretation, this study provides a ground truth example and insights into the degree of accuracy microseismic can offer as a technology in discerning the efficacy of modern completions.

Introduction

The Hydraulic Fracture Test Site (HFTS) in Reagan County, Texas consists of 11 horizontal development wells in the Wolfcamp Formation along with two preexisting Wolfcamp wells which were refrac'ed on the eastern side of the package (Figure 1) (Courtier et al, 2016, 2017). The primary objective of the HFTS throughout the course of testing was to evaluate subsurface controls and operational impacts on hydraulic fracture geometry and completion efficiency, with one of the main undertakings of the project involving the drilling and coring of a slant well between two of the completed wells in the package in order to determine the presence and distribution of hydraulic fractures and proppant.

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