Abstract
This paper describes the field application of a novel wireline conveyed cased-hole formation dynamics tester designed to drill a hole in casing, measure formation pressure and permeability, identify and retrieve downhole fluid samples and seal the hole with a bi-directional plug. Until recently the only way of obtaining such information in cased hole was either by performing a DST or using a modified open-hole tester (needing explosives and squeeze cementing).
The Sembakung field, N.E. Kalimantan was discovered in 1975 and has produced over 37 MMBO. The main producing interval is the Upper Middle Miocene Tabul formation. Over 35 separate sands have been identified in this highly stratified reservoir and producing wells have multiple commingled zones. The reservoir and crude quality is good (ϕ=15–30%, K=200–2000 mD, 37 API, low-sulphur low-wax).
Equatorial Energy acquired an 80% stake in the TAC in 1998 and commenced an aggressive program of infill drilling, as well as acquired a 3-D seismic survey in 2001. 3D seismic uncovered the presence of a significant southward structural extension with additional exploration potential. It also revealed the existence of new untapped reservoirs and structural compartmentalization within the field. Declining pressures and signs of inter-well communication indicated the urgency of field pressure maintenance.
Drillstem testing was not feasible as a large number of potential zones needed to be tested. This novel tool proved useful in managing the challenge. The tool was run successfully in 7 wells where it drilled and tested 71 holes in casing and recovered fluid samples. Formation pressures were measured, permeabilities estimated and fluids identified using downhole pumpout with optical spectroscopy. The performance conclusively demonstrated the applicability and cost-effectiveness of this novel technique in revival of this oilfield.
