Acid Soluble Plugs – Pressure Tight Solution for a Pre-Perforated Liner

Abstract

This paper covers the development, laboratory testing, and field testing of Acid Soluble Plug (ASP) technology as a viable completion alternative to wireline or tubing conveyed perforating. The ASPs are installed in a pre-perforated reservoir liner and dissolve when soaked in acid allowing access to the reservoir. This allows the technology to be easily applied in reservoirs where matrix acid jobs or acid fracturing techniques are employed. The ASP technology was developed to reduce risk and cost associated with wireline and tubing conveyed perforating. ASPs were designed, manufactured, and field tested in both 5 in. and 7-5/8 in. reservoir liner sizes for wells in the Ekofisk and Eldfisk fields. The combination of laboratory testing and large scale field testing influenced the design of the ASPs as well as the additives utilized in the acid systems used to dissolve them. From concept to initial field implementation, the process of ASP engineering development took more than two years. The concept was initially field tested in deviated injectors with ASPs installed in the deepest section of reservoir liner. The field tests proved the ASP concept prior to depending on the technology in a horizontal producer with an un-cemented, liner-in-liner completion solution. The field tests showed that acid soaking dissolved the ASPs in the down hole environment and allowed efficient acid stimulation of the reservoir. It also reduced the number of wire line runs necessary to complete the well. When field tested in a liner-in-liner completion application, installation of the ASPs in the reservoir liner eliminated tubing conveyed perforating runs. The reservoir liner was un-cemented with mechanical openhole packers for zonal isolation. The ASPs provided a pressure tight reservoir liner to set the packers against and eliminated fluid loss during the running of the inner completion string. Optimization of this technology is an ongoing process. The plug design itself continues to evolve as well as the operational steps to minimize the soaking time necessary to dissolve the plugs and gain access to the reservoir. The latest field applications will be shared at the time the paper is presented.