Successful Application of Horizontal Well Completions for Development of Low Permeability Gas Reservoirs in a Complex Fluvial Deltaic Environment - A Case Study

摘要

VICO Indonesia is the operator of the Sanga-Sanga Production Sharing Contract located onshore of the Mahakam delta, East Kalimantan, Indonesia. The PSC has produced over 70% of the OGIP (original gas in place). The fields are relatively mature with the remaining gas resources locked up in either pressure depleted reservoirs or in low permeability reservoirs where conventional techniques have not been very effective in depleting these resources. During 2006, VICO decided to perform a pilot development of the larger/tighter reservoir tanks, utilising the horizontal completion technique as the preferred completion approach. To date VICO has successfully drilled and completed 5 horizontal wells, one in the Semberah field (S77H) and four in the Nilam field (N228H, N230H, N238H & N240H). The Semberah S77H well was drilled and completed in 2006 at a relatively shallow depth (~ 8000 ft.TVD.SS), in order to demonstrate the applicability of horizontal drilling technology within VICO. The four subsequent wells were drilled in the Nilam field, to depths of ca. 12,500 ft.TVD.SS. The N228H & N238H wells were drilled to test the productivity of horizontal wells at higher reservoir pressures; where condensate banking was thought to be a contributory factor to the dramatic transient and low deliverability seen from conventional vertical wells. Whereas the N230H and N240H wells, were drilled to test the productivity of horizontal completions in the depleted tanks where condensate banking may not be such a significant factor. All five of the wells are currently producing at relatively stable rates with significantly less decline, when compared to conventional offset wells. The initial gas production rates, that were achieved, were significantly higher than conventional wells producing from the same reservoirs and the total reserves recoverable per well are estimated to be 2 - 3 times higher than a conventional well. The paper will describe in detail the candidate selection criteria, well design, well placement, drilling risks, tool reliability and the challenges steering a horizontal well in a geologically complex environment with high degree of reservoir uncertainty.