Evaluation of Oily Waste Injection Below the Permafrost in Prudhoe Bay Field

Abstract

This paper presents the results of an extensive study and field test carried out at the site of Prudhoe Bay’s four oily waste injection wells. Prudhoe Bay’s four oily waste injection wells. The field work was part of an overall environmental assessment intended to: 1. confirm earlier results indicating that no fluid communication was occurring with the permafrost; 2. determine optimum conditions for the disposal of waste in the presence of hydraulically-induced fractures; 3. substantiate that an increased injection pressure could be safely implemented. A three day injection test, including a step-rate stage, was carried out. Data collected included surface and downhole pressures, in-situ stress measurements, and pressures, in-situ stress measurements, and monitoring of ground surface deflections and wellbore hydraulic impedance. Radially symmetric surface tilt patterns showed that the test well connects to a horizontal fracture of 60-foot radius. Wellbore impedance indicated that a horizontal fracture with 9–18 foot radius communicated with the well. Integration of rock mechanics, historical information, and the collected data provided a clear picture of what was occurring underground. The different evaluation techniques showed consistent results as reflected in the estimated fracture size, placement and damage zone properties. properties.