Natural gas sweetening via H2S, H2O, and bulk CO2 removal.
Denison Gas acquired a gas treatment facility that receives natural gas from several sources. Four banks of primary membranes treated the feed stream, reducing CO2 content from a typical 30% to 10%. The nonpermeate stream is mixed with dehydrated gas from other fields, containing approximately 13% CO2. The combined gas undergoes compression and further pretreatment before entering two trains, each containing three banks of final membranes to reduce the CO2 concentration to a sales gas specification of 3%.
The existing third-party cellulose acetate (CA) spiral-wound membranes were experiencing accelerated degradation. Of the just over 7 MMcf/d processed, almost half—3.5 MMcf/d with 47% CO2—was lost through flaring, resulting in a low hydrocarbon recovery of <67%. With new wells being brought online, facility throughput was expected to increase in the near future. The operator wanted a robust membrane technology that is capable of continuous long-term operation and would deliver the required product specification. Minimizing flaring and venting of permeate gas and using the existing membrane infrastructure were other key requirements.
After thorough assessment and site inspection, Schlumberger proposed Apura gas separation membranes from FUJIFILM. Continuing its efforts to advance acid gas treatment technologies, Schlumberger has entered into an agreement with FUJIFILM to further develop and market the Apura membrane. The durable spiral-wound multilayer composite membrane promotes higher gas throughput, provides excellent CO2 removal, retains maximum hydrocarbons in the product gas, and has a longer operating life. It enables simple plug-and-play replacement of CA spiral-wound membranes, without any skid modifications. With an extended life in water-rich conditions, Apura membranes are also ideal for the varying levels of upstream gas dehydration handled by this facility.
Initially, Denison Gas replaced two banks of primary and two banks of final membranes. This change almost halved the volume of gas flared, reducing it from 3.5 MMcf/d to 1.8 MMcf/d, while the concentration of CO2 in the permeate stream increased from 47% to >87%. The result was a vastly improved hydrocarbon recovery rate, which rose from <67% to a notable 96%, significantly increasing the operator’s gas revenue and enabling them to recoup the cost of the membranes within just 6 months. Additional membranes were replaced a year later, expanding capacity to meet the demands of increased drilling and production.
“Schlumberger was chosen due to
The new elements have greatly increased our plant’s profitability, and still performing well after 2 years of service.”—Tim Petersen, Chief Operating Officer, Denison Gas
Denison Gas replaced deteriorating 3rd-party membranes at its gas treatment plant with robust Apura composite membranes, increasing natural gas recovery, and hence revenue, by >40%.