RIASSUNTO
IADC Member
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Abstract
ARCO is currently engaged in a comprehensive field project to demonstrate the use of hydraulic fracturing for solid waste disposal. Implementation of this research program includes drilling of three 5000' test wells: an injection well and two offsetting monitor wells that each contain twenty-five 3-component geophone pods for passive seismic fracture detection. This paper focuses on the data gathering during drilling operations and the unique drilling challenges required for this disposal demonstration project. Specialized data was required for assessment of fracture geometry and containment, measurement of fracture azimuth to site the monitor wells and verification of formation seismicity for fracture diagnostics. This information was obtained with extensive coring operations, open- and cased-hole micro-fracs, and an injection test to directly measure the formation seismicity. Drilling challenges included the placement and cementing of the 750' of geophone pods and 4250' of armored transmission cable in each monitor well, plus redesign of well plans due to wellbore stability problems.
Introduction
The use of hydraulic fracturing for disposal of drill cuttings and other production wastes has become increasingly popular over the last five years. Annulus injection of oil-and water-based drill cuttings is routinely used in the Gulf of Mexico, Alaska, and the North Sea. In the past two years, fracturing has also been used for disposal of Naturally. Occurring Radioactive Material (NORM) by both Shell and ARCO in the Gulf of Mexico, and by ARCO and BP at the Prudhoe Bay Unit in Alaska. With these new applications of hydraulic fracturing in mind, ARCO has undertaken a major field research program to demonstrate the feasibility of fracturing for industrial solids waste disposal.
This project, called the Deep Well Treatment and Injection (DWTI) Program, has recently completed field operations in Jasper County, Texas. A total of 3 million pounds of sand, 1 million pounds of bentonite and 50,000 bbls of water was injected into the Lower Frio Sand over a period of five days. The fracture growth was monitored with several fracture diagnostic techniques, including RIA and temperature logs, surface tiltmeters and hydraulic impedance testing. As part of the program, a state-of-the-art micro-seismic data acquisition and locating system was developed, which performed real-time event detection and location processing on-site. Two monitor wells, at distances of 80 and 500' from the injection well, each contained 75 geophones that measured the seismicity from the propagating fracture. Other technical elements of the DWTI program included fracture model development, waste characterization testing and ultimate fate modeling.
The focus of this paper is on the specialized data gathered and unique drilling challenges posed by the three wells drilled for this project.
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