A full logging suite was acquired, including formation pressure measurements, confirming a 33 ft gross gas pay zone (30 ft net) with formation permeabilities calculated to be over 1 Darcy across the best quality zone. The pressures and gas-water contact depth in Tambak-2 are the same as those encountered in Mako South-1, confirming a very large “single-tank” or areal extent of the Mako gas field.
While preparing for a Drill Stem Test (DST) across the intra-Muda reservoir, an inflatable open hole bridge plug (packer), used to isolate the gas-bearing reservoir for testing, failed. During operations to recover the packer, the well started flowing natural gas to surface. For safety reasons, the well was immediately shut in. Subsequently, utilising the appropriate well control practices, the well was killed using heavy mud containing barite. A significant quantity of the heavy mud was lost in the highly permeable Intra-Muda reservoir. Following this operation, the well was conditioned, and the DST equipment set-in place into the wellbore. Two separate DST attempts failed to flow gas to the surface due to the heavy formation damage from the kill mud.
Miltos Xynogalas, Conrad Executive Director/CEO, commented: “The Tambak-2 well is an appraisal well of the Mako gas field accumulation located a significant distance from the Mako South-1 gas discovery and has delivered a result better than our pre-drill expectation. The result is likely to have a positive impact on Mako’s gas-in-place and potentially recoverable volumes. Uncertainty in these parameters has been greatly reduced. The well confirmed the lateral extent of the high-quality reservoir and the presence of a continuous hydrocarbon accumulation. Initial petrophysical analysis suggests high gas saturations, while the gas mobility encountered during pressure measurements and the flow of gas while retrieving the packer confirms the ability of the hydrocarbons to flow to the surface. While the unsuccessful DST caused by the formation damage is disappointing, the well results are extremely encouraging for the development of the Mako gas field. Petrophysical analysis suggests any DST testing would have yielded similar high flow rates to the discovery well.”
Tom Kelly, Empyrean CEO commented: “A valid flow test at Tambak-2 without kill mud being required due to the packer failure would have been desirable given the excellent quality reservoir seen on logs and the 33 feet of net gas pay. The logs confirm an excellent quality reservoir at an approximate 13.5 km step out from Mako-South 1. This achievement alone is expected to have a positive bearing on resources and potential reserves. We now move on to Tambak-1 which in addition to appraising the intra-Muda sands of the Mako gas discovery, will also test the deeper lower Gabus target”.
Read the article online at: https://www.oilfieldtechnology.com/offshore-and-subsea/28102019/tambak-2-well-closed/
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