The Modelling, Application, and Monitoring of Scale Squeeze Treatments in Heterogeneous Reservoirs, North Sea

Abstract

Abstract Scale control within produced fluids as water follows the cycle of injection, production, processing and reinjection in oil/gas production facilities is critical to the effective production of hydrocarbons in a safe, economic and environmentally acceptable manner. This paper will focus on the scale challenges associated with seawater injection into two North Sea reservoirs with a moderate Barium Sulphate scale challenge (80 to 220 ppm Barium, seawater injection) and will describe the impact of scale ion reduction from injection to production wells and the lower minimum inhibitor concentration that results The paper will outline the selection of the inhibitor chemical for squeeze application, initially via bullhead application of the squeeze treatment without diversion then development of a diversion methodology in conjunction with production logging tool data. The paper outlines the application of the diversion treatment applied via bull heading and the improvement in treatment life as well as treatment economics that resulted in the heterogeneous formation. The paper will clearly demonstrate using the four squeeze treatments to a single well how squeeze treatments can be enhanced without the need for coil tubing to allow selective placement. The design methods for this diversion technology will presented along with the methods of monitoring such treatment to ensure effective placement was achieved with the use of inert tracer, produced water analysis, evaluation of type/amount of suspended solids and inhibitor residuals. Introduction Field Description The field is located in the UK sector of the North Sea, 200 miles North East of Aberdeen. The A platform began production in June 1976 and the B platform in July 1984. The wells produce oil, gas and water from Jurassic sandstone formations. The reservoir temperature is approximately 100oC. Scale formation has been a production issue in these fields as they are supported by injection of seawater and the formation brines contain up to 220 ppm barium and up to 300 ppm strontium ions, Table 1. Wells with seawater breakthrough are scale squeezed using a phosphonate scale inhibitor to control sulphate and carbonate scale formation.