Developing Oil in Monobore Well Completion Using Permanent Coil Tubing Gas Lift Application

Abstract

Abstract VICO Indonesia has operated the Sanga-Sanga PSC in East Kalimantan, Indonesia, since 1968. More than 750 development wells have been drilled to date in the complex Mahakam Delta in East Kalimantan. The mature reservoirs are predominantly gas, extremely depleted and have an average recovery factor of about 70%. To optimize the development cost VICO changed the completion from multi string and multi packers to monobore in 1997 and furthermore to dual monobore in 2005. VICO has also focus to optimize oil production and recovery. The current oil recovery factor is relatively modest and needing further detail study and optimization. A multi-disciplinary team was performed to further evaluate oil potential in all VICO fields including review of historical performance, geology and development opportunities. These reservoirs were also evaluated using material balance to understand the initial volumes in place, the drive mechanism and the opportunity to maximize production and oil recovery through the existing wells. One of the challenges in maximizing oil recovery is artificial lift system in monobore completion. VICO has evaluated and selected gas lift as optimum artificial lift method. There are two possibilities to gas lift oil wells (1) using a side pocket mandrel in the conventional dual string completion and (2) inject gas lift through coil tubing in the monobore completion. The paper describes innovative gas lift system in monobore completion where gas lift mandrels were not pre-installed. This technique has been implemented, by running 1.5" coil tubing into a well through a special tubing hanger attached to the top of the Christmas tree. This technique allows gas lift to an oil reservoir in monobore well completion without requiring rig for recompletion. This application is known as "Permanent Coil Tubing Gas Lift" or PCTGL. This technique has been implemented in "MUT-X" well that was not capable to flow naturally, and then PCTGL was installed to resume oil production. The well was flowing 600 BOPD initially and now is continue flowing at 350 BOPD. In summary, PCTGL is a proven favorable and simple method for artificial lift application in monobore completion to maximize oil production and recovery. Furthermore, this technique has helped VICO in synergizing gas and oil development to maximize value of the assets.