RIASSUNTO
Abstract
Total E&P Indonesie (TEPI) is the main gas producer in Indonesia which produces around 1900 MMscf/d of gas. One of the challenges is to maintain its production plateau under liquid loading issue. Almost half of TEPI gas production comes from liquid-loaded wells, representing 85% of total producing wells in the affiliate.
Up until recently, dewatering activity in TEPI is only performed by means of regular offloads; involving substantial means. These operations present specific risks not only for safety and assets but also for environment by flaring of gas through testing barge.
A cross functional team has been established to find out innovative solution based on the “Foam Assisted Lift” (FAL) principle and enabling to keep existing DHSV in the well completion. The FAL principle consists in offloading the wells by creating foam down-hole through continuous injection of surfactant to help liquid lifting and gas breakthrough. This paper describes Capillary String Injection System that can be fitted into existing wells, using existing DHSV control line for surfactant injection while keeping its primary safety function as a fail-safe device. The installation equipment includes a modified wireline-retrievable surface-controlled sub-surface safety valve (WR-SCSSV) with capillary tubing attached below it. Injection operates via existing control line of the safety valve to inject chemicals, does not require any further wellhead modification. In addition, this system fits perfectly with the context of mature field; simple, cost-effective, safe and easy to handle.
Introduction
Liquid loading of gas wells is one of Total E&P Indonésie (TEPI) main challenges. It is the phenomenon of inability to lift liquids out from the gas well. Liquid therefore starts to accumulate in the borehole, increasing significantly the hydrostatic pressure. Gas rate will drop significantly as a result. Then, self-killing process starts. The wells are in loading mode when the produced gas is below critical rate,I t is the so-called “Turner Rate”. Almost half of TEPI gas production comes from wells prone to self-killing.As of April, 2014; it represents 85% of the total producing wells in the affiliate. Therefore recovering all reserves from very weak wells, and from “supposed dead” wells, is the challenge of this technology.
Until recently, dewatering of wells in TEPI is performed by means of regular offloads by flaring, involving substantial means (testing barges and personnel). Offloading is done by connecting the well to a testing barge, and setting the wellhead pressure at the lowest pressure possible (equal to atmospheric pressure). These operations present specific risks, not only for safety of personnel and assets, but also for the environment when flaring gas through the testing barge, which results in Green House Gas (GHG) emissions. Moreover, they remain “spot” treatments that do not tackle the cause of liquids loading and have only a temporary effect on production gains. Other conventional offloading solutions such as plunger lift, wellhead compressor, velocity string and gas lifting cannot be applied due to either economical factor and/or because of incompliance with TEPI Rules.