Field-wide Interference Test for Understanding the Hydraulic Communication between Two Stacked Reservoirs

Abstract

A field-wide interference test was recently conducted to delineate the hydraulic communication between two large carbonate reservoirs separated by a thick non-reservoir formation. The reservoirs were newly developed with peripheral water injection for pressure support. This initial development stage provided an opportunity to take advantage of the undisturbed state of the two reservoirs during field commissioning to conduct this interference test prior to production. The injection start-up was, therefore, designed to inject into one reservoir while monitoring pressures at various parts of the other reservoir. Several observation wells across the field were designated to record the pressure changes during the initial water injection stage to provide the field coverage. The injection rates were also closely monitored and modified throughout the test period to record the rate of pressure change in the observation wells.The field was developed with the state-of-the-art permanent downhole monitoring systems (PDHMS) which provided the means for comprehensive monitoring of this field-wide interference test. The test showed some interesting findings within the reservoirs themselves, areas of communication were indentified and the extent of the lateral connectivity was observed. Additionally, the dynamic data acquired during this interference test will complement the static data for building improved geological and engineering models.This paper describes the test design, implementation and presents the results and findings. The test was concluded but monitoring is continuing utilizing the intelligent field (I-field) infrastructure and the results will, in future, be incorporated into reservoir simulation models for production/injection strategy optimization and accurate field performance forecasting. OTC 20571opportunity of the undisturbed state of the reservoirs, utilizing the readily available injection system, to conduct the test. The enabler was the leading-edge technologies implemented in the development.The following conclusions are drawn from the results of this field-wide test:• In addition to the central part of the field where the communication was discovered in the past, pressure communication between these two reservoirs was also seen at the southern end of the field, as this could be detected during the relatively short period of this test. • No significant pressure increase was seen in the east side suggesting no communication or very weak channels of communication in that area. • The degree of inter-reservoir communication at various parts of the field was assessed using the interference test results.With the conclusion of this field-wide interference test, the results will be used to adjust production/injection plans in both reservoirs in order to maximize hydrocarbon recovery. The potential risk of water encroachment from Reservoir B into Reservoir A will be minimized by this knowledge of more areas of communication.