Abstract

Lagan field was discovered in 1988 and is located in South Sumatra, Indonesia. Lagan is a gas field that consists of 30 wells and produces from 7 different sand layers with three faults. Along with reservoir pressure depletion, the pressure system was reduced as a strategy to maintain the gas production. In 2009, it was discovered that sand was being produced and was eroding surface control equipment during system conversion from medium pressure to low pressure.

Due to limited core data, the initial challenge for conducting a sand control study was to identify which wells and which layers were producing the sand. To resolve this problem, four wellhead de-sanders were installed at four different wells, all of which produced from different sand layers. The next challenge was to find and apply a suitable sand control method by considering the urgent need to accelerate the application of sand control, limited well accessibility and rig mobility due to field location and road conditions, cost and application effectiveness. Wellhead de-sander was eventually selected as the most suitable sand control method for this field. The design and fabrication of the wellhead de-sander were completely in-house and were continuously improved to enhance the quality and quantity of sand trapping.

After one year’s application, the wellhead de-sander has proven its effectiveness by reducing the amount of sand carried out to the station, decreasing production separator downtime, and eliminating surface control equipment failure cases. Until now twelve wellhead de-sanders have been installed in Lagan field to increase gas production reliability, with a total cost saving of up to USD 648.000. This paper elaborates on the road map for the sand control study and its application in a multi- layered reservoir gas field with limited subsurface data, explains how well-modeling was used to estimate the strength of sand consolidation, and describes the step by step process for optimising wellhead de-sander design.

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