Acoustic Signal Analysis for Sand Detection in Wells with Changing Fluid Profiles

Abstract

Abstract Sand production can be a severe problem in the East Coast oil and gas fields of Trinidad. Geologically young formations in this region exhibit little to no natural cementation forming very weak unconsolidated sandstones that often lead to sand production. With the increasing drive to increase production rates, the accepted draw down limits for these reservoirs may be tested. As a result surface monitoring and early detection of sand production has become extremely important in providing further assurance to mitigating potential incidents due to sand production resulting from excessive draw downs. For this project, data collected from thirty acoustic sand -detector calibration trials done in three fields offshore East Coast Trinidad, was analysed to investigate the accuracy of the sand detector in predicting sand concentrations in different fluid profiles. From this study, a simple model is being proposed which can predict sand concentration for sand particles ranging between 30 to 120 microns at any given fluid profile using an acoustic sand detector. This model may be used in the absence of a calibration plot and when the flow profile of a well is changing, to accurately predict sand concentration. The results from this project can provide the operator with greater assurance when optimising production rates, especially in wells that have a tendency to produce sand. Introduction To prevent a high potential incident from occurring several fields in Trinidad have installed a sand detection system which use non- intrusive acoustic sand detectors. Installation of a system to monitor and quantify sand production from a well would be invaluable to assist in optimizing well productivity and to detect sand as early as possible. Early detection would then lead to possible remedial action that could prevent incidents due to erosion and improve production. The prediction of a maximum sand free production rate offers several benefits, but this is not always possible due to the changing nature of the fluids produced as the reservoir is depleted. This report examines the recent advances in sand detection and attempts to develop a new correlation to predict sand concentration levels in changing fluid environment. Sand production, if left unchecked can lead to tubular erosion, surface equipment failure and eventual hydrocarbon spillage, or leakage into the environment, see figures 1and 2, with the consequent safety risks.