An Innovative In-situ Natural Gas Lifting Approach to Produce High Pour Point Oil with High Output: A Case Study

Abstract

Abstract This paper demonstrates an innovative in-situ natural gas lifting approach, which has been successfully applied in AG pool of FN field, Sudan. AG pool is a series of edge water driven stacked sandstones with light oil and natural gas pools, and mostly natural gas zones are below oil zones. AG oil is typical of high pour point, ranging from 37 to 57 Celsius degree. Possibility of wax deposition posed great production and operational challenges at 27 Celsius degree surface temperature. Gas below oil pool could serve as in-situ gas lifting to boost production and reduce wax deposition. This process undergoes tubing produced natural gas flowing simultaneously into annular to lift oil production in the same wellbore. This process has been optimized by following approaches: 1) establishing screening criteria of qualified gas and oil zones for lifting; 2) Partial completion and reduced perforation density in gas zones for controllable gas rate; 3) Separators deployed to remove portion of gas for smooth transportation to facilities. 4 producers have undergone in-situ gas lifting since 2009, average well output achieved 2 to 4 times of DST rate, amounting to 2000 to 4000 BOPD with low water cut. Up-efficiency has been above 85% without wax deposition problems. Operational costs were greatly reduced. Conclusions drawn from successful in-situ gas lifting application were:1) selected oil and gas zones fully qualified for gas lifting; 2) optimized in-situ gas lifting brought high output and low water cut; 3) innovative wellbore structure and facilities design replaced the use of pumps and saved costs. Sudan is abundant in stacked oil and gas pools with high pour point, therefore in-situ gas lifting has wide applications. Successful in-situ gas lifting in this paper highlighted significant oil rate gain without oil gelling problems, cost-effective wellbore structure and facilities design, give a staircase for future wider applications.