The DST flowed dry gas from the intra-Muda sands at a rate of 11.4 million ft3/d on a 181/64-in. (2.8 in.) choke, maintaining a wellhead tubing pressure of 225 psi. The DST of the Tambak-1 well was completed with cased hole perforations along a 6-ft interval. The DST demonstrates that this completion method is viable, having resulted in the maximum flow rate mentioned above, again confirming the deliverability of the Mako reservoir. Cased hole perforation is simpler and a more costefficient completion method than the openhole screen completion used to successfully test the Mako South–1 well (located 4.9 km from Tambak-1) in June 2017.
Tambak-1 encountered a very well-developed 56 feet thick sand package of high permeability and good porosity, significantly thicker than the 33 ft of pay discovered in Mako South-1.
The Tambak-1 well intersected the intra-Muda reservoir (Mako gas field) at a depth of 1276 ft subsea, and Conrad recovered a full suite of wireline logs, together with a pressure survey and fluid and gas samples. With the better-than-expected flow test, the data confirmed that the Mako gas field is a very large (350 km2), aerially extensive “single tank” field, supporting the conclusions from the recently drilled Tambak-2 well, over 17 km from Tambak-1.
Tambak-1 was designed to appraise the northeast flank of the Mako gas field and to explore the lower Gabus formation at approximately 5063 ft subsea, directly below the Mako gas field. Several stacked sands with strong gas shows were encountered within the Lower Gabus formation as prognosed. Results of wireline logging, pressure tests, and hydrocarbon samples throughout the formation have established that the reservoirs are not commercial. However, the exploration results provide further evidence of an active petroleum system, which is encouraging for future exploration upside within the Duyung PSC.
The Tambak-1 well is currently being plugged and abandoned, prior to the COSL Asian Endeavour 1 rig being demobilised.
Miltos Xynogalas, Conrad’s CEO said: “This has been a tremendous result for the drilling campaign as a whole, confirming a very large single tank gas accumulation, connecting Tambak-1, Mako South-1 and Tambak-2 over a long distance, demonstrating beyond any doubt the mobility and deliverability of natural gas throughout the field. Our first well in this drilling campaign, Tambak-2, encountered 30 ft of high-quality gas-bearing intra-Muda sandstones, representing a better developed reservoir than seen in Mako South-1. It also confirmed a common gaswater contact and pressure system across the Mako structure.
Tambak-1, designed to appraise the field limits, yielded better than expected results. The well encountered 56 ft of excellent quality intra-Muda sandstones, penetrated the gaswater contact within the reservoir section, and encountered 20 ft of sandstones within the gas leg. The gas-water contact was clearly common in all wells on the Mako structure to date, and a common pressure system across the field has been confirmed.
Our efforts will now move to the optimisation of the approved Mako Plan of Development working in close collaboration with our partners and the Indonesian authorities.
The entire Conrad team has worked tirelessly over the past 70 days to complete another campaign, maintained a 100% health and safety record, on time and on budget. Overall, the drilling campaign has delivered results that should significantly increase the resources of the field.”
Read the article online at: https://www.oilfieldtechnology.com/offshore-and-subsea/22112019/appraisal-and-flow-test-completed-at-tambak-1-well/