The Lukut Updip-1 (LKU-1) well in Brunei Block L has flowed gas continuously from two intervals that have not previously been penetrated by any wells onshore Brunei, Serinus Energy Inc. said in a news release.

While the rates were estimated at less than 50,000 cf/d, the discovery of hydrocarbons within these zones indicates that further analysis and appraisal will be required to evaluate the resource potential of this play, the release said.

Test 1: The LKU-1 well encountered a drilling break and a significant influx of gas with a total gas reading of 47% whilst drilling 6-in hole starting at a depth of approximately 2,131 m (6,991 ft) measured depth (MD) and continuing to a depth of at 2,137 m (7,011 ft) MD, the last 3 m (10 ft) of which is interpreted to be clean sand, the release said. C1 gas readings peaked at 332,000 parts per million (ppm) and C5 gas readings peaked at 628 ppm at TD, according to the release.

Pressures rose significantly, and there was material gas influx with total gas readings increasing to 47% which resulted in gas being flared at surface for several hours. The mud weight was subsequently increased to 17.7 pounds per gallon (ppg) to control the calculated formation pressure of 5,366 pounds per square inch (psi), Serinus said. Due to the significantly higher than expected formation pressures and equipment limitations, the company determined that it could no longer safely continue to drill the LKU-1 well and, consequently, a cement plug was put in place from 2,120 m to the total MD of 2,137 m (7,011 ft) and 4.5-in casing was set to a depth of 2,120 m (6,955 ft). The initial planned depth for the LKU-1 well was 2,959 m (9,708 ft) MD and 2,410 m (7,877 ft) TVD.

The first zone to be tested was the bottom 6 m of the well from 2,131 m (6,991 ft) to 2,137 m (7,011 ft) MD over which the cement plug had been placed, the release said. Gas flowed continuously at a low rate during the test. The formation is believed to have been damaged by heavy drilling fluid, mud system additives, and cement during the drilling process as the drilling team worked to control the high pressures encountered. Attempts to clean up the perforated interval by utilizing an acid treatment were not successful.

Test 2: During the drilling operation, a general trend of increasing silt and/or sand content was observed from a depth of approximately 1,890 m (6,201 ft) and continuing to 2,137 m (7,011 ft), the release said. The sandy/silty shale encountered over this section appears to be hydrocarbon charged, with C1 to C5total gas readings increasing from a 10-m (33-ft) average of 0.49% at 1,700 m (5,577 ft) MD to a 10-m (33-ft) average of 8.1% at 2,110 m (6,923 ft) MD. C1 gas readings steadily increased from a 10-m (33-ft) average of 3,150 ppm at 1,700 m (5,577 ft) MD to a 10-m (33-ft) average of 58,000 ppm at 2,110 m MD. Based upon the increased pressures and associated hydrocarbon shows, the thick silty shale zone was selected as the second zone to be tested.

A total of 60 m (197 ft) was selectively perforated between the depths of 1,980 m (6,496 ft) and 2,120 m (6,955 ft), according to the release. Gas was flared at surface throughout the test but the well did not produce at commercial rates. The entire section tested in the second test, which was open during the well control efforts, is believed to have also been damaged by drilling fluid and mud additives.

The section of the LKU-1 well below approximately 1,100 m (3,609 ft) MD has not previously been penetrated by any wells in onshore Brunei. The drilling break at 2,131 m (6,991 ft) MD is interpreted to correspond to the top of a zone defined by seismic (the green zone) that was a secondary target of the well, according to the release. The deeper primary target of the well (the red zone), which the company expected to encounter at 2,402 m (7,881 ft) MD, has not been penetrated.

The green zone, the transition zone above the green zone (Test 2), and the red zone are all interpreted to be facies associated with turbiditic sandstone deposition which are likely to extend over a large area, according to the release The company believes that the tested formations may be capable of producing at commercial rates, and that further analysis, evaluation and appraisal will be required to fully assess the prospectivity and productivity of this new play.

Serinus has a 90% interest in Block L with indirect wholly-owned subsidiary Kulczyk Oil Brunei Ltd. having a 40% interest and indirect wholly-owned subsidiary AED South East Asia Ltd. (operator) having a 50% interest, the release said. The remaining 10% interest is owned by a private Brunei company at arm’s length to Serinus.