Characterization of a Remotely Intersected Set of Hydraulic Fractures: Results of Intersection Well No. 1-B, GRI/DOE Multi-Site Project
Authors: Branagan P.T. , Peterson R.E. , Warpinski N.R. , Wright T.B. 
Published: December 2007

A deviated observation or "intersection" well (IW 1-B) was drilled, cored, logged and tested through an area in a fluvial sandstone reservoir that had previously been hydraulically fractured. The point of intersection with the fractured interval was located 126 ft from the fracture well along one wing of the fracture(s) at a measured depth of 4,675 ft.

Direct observations from core and borehole imagery logs in IW 1-B indicate that a total of 11 far-field vertical fractures were created. Clustered in a narrow 2.6-ft-wide interval, these 11 fractures are the direct result of 6 experimental fracture treatments executed in the distant frac well over a 4-month period. Diagnostic data acquired through IW 1-B included direct core observations and measurements, borehole log imagery, gamma ray (GR) tracer identification, well-to-well pressure transient and fracture conductivity tests, and production logging surveys. The explicit intent in the emplacement of IW 1-B was to provide direct observations and information to characterize the hydraulic fracture(s) in support of a remote-sensing fracture diagnostic program that included microseismic monitoring and inclinometer measurements.

Introduction

Research being conducted as a part of the Gas Research Institute (GRI) and Department of Energy (DOE) Multi-Site (M-Site) Hydraulic Fracture Diagnostics Project has focused primarily on the development of a microseismic fracture mapping capability. As such, a series of hydraulic fracture injections and associated diagnostic data acquisition activities were conducted in a fluvial sandstone reservoir, designated the B Sand, at a nominal depth of 4,540 ft. Comprehensive diagnostic instrument arrays including 30 triaxial microseismic packages and 6 biaxial inclinometers were permanently emplaced at depth in Monitor Well No. 1. A 5-level wireline-retrievable microseismic array was employed in MWX-3.

Figure 1 provides a plan view of the M-Site detailing project-related well locations and the predicted hydraulic frac azimuth. Data analyses of microseismicity associated with the fracture process zone provided plan and profile map views of the fracture, while FRACPRO simulations and inclinometer results yielded correlative dimensional frac characteristics, e.g., length and height.

Following a series of six separate injections involving fracture mapping experiments, the B-Sand research program plan scheduled the drilling of a deviated wellbore designed to intersect one wing of the hydraulically fractured interval approximately 130 ft from the MWX-2 treatment well. The intent was to use direct observation of a hydraulic fracture(s) to provide a measure of ground-truth concerning certain aspects of the microseismic mapping technique's accuracy and the inclinometer-derived frac characterization. It would also facilitate the assessment of results from 3D and other types of hydraulic fracture model predictions.

This hydraulic fracture intersection well, IW 1-B, also provided project scientists a unique opportunity to observe and describe the far-field character of the induced hydraulic fracture(s) and to conduct other fracture technology experiments. The employ of five different radioactive (RA) tracers in four of the treatments and the use of three different colored proppants afforded a tagging process that would aid in defining the origin of any remotely intersected fracture(s). Moreover, this process would provide complimentary information regarding hydraulic fracture dimensions and proppant placement. The supporting information verifying that hydraulic fractures were intersected, the character of the hydraulic fractures, fracture genesis, proppant placement, and proppant conductivity are the primary emphasis of this paper.

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