Abstract

In early 2006 Chevron International E&P drilled and completed the first multilateral well in the Gulf of Thailand. Routine development drilling in the Kaphong Field of the Pattani Basin unexpectedly discovered two production horizons that possessed reservoir characteristics and sufficient oil reserves to make each a viable horizontal well candidate. At the time, however, only a single drilling slot was available on the platform; thus, dictating that only one well bore could be drilled to tap both reservoirs. Further complicating the problem was the fact that the drilling rig which discovered the horizons would be moving to a new platform a short 5 weeks after it was understood by reservoir engineers, geologists and geophysicists that multiple horizontal well candidates existed.

This paper chronicles the rapid processes that took place to evaluate, plan and execute the first multilateral well in the Gulf of Thailand. More importantly, though, this paper captures the unintended consequences (both good and bad) that came with executing this project so quickly. This includes an analysis of how decision making, project planning and ultimate execution where affected by the short time window available. From this we discuss lessons learned that may be universally applicable when rapidly expanding the use of technology in a remote region of the world (regardless of how small that expansion is).

Introduction

The Pattani Basin in the Gulf of Thailand is a region containing significant oil and gas reserves. Chevron Thailand has been producing from this basin since 1981. Although predominantly a gas producing region, the northern sector of the Pattani Basin is oil-rich and has been the focus of significant development in recent years. The push for greater oil development has lead to sizable production increases in the last 4 years. One key component to these production gains is the use of horizontal well bores. Although only 20 stand-alone horizontal wells had been drilled prior to drilling the multilateral well discussed in this paper, they collectively contribute 11% of the 107,000 bbls/day oil production from Chevron's Gulf of Thailand operation while making up only 4% of the well count.

With the strength of their oil-rate contribution it makes sense that Chevron Thailand would want to drill as many horizontal oil producers as geologic reality would permit. It is within this setting that Chevron Thailand unexpectedly found two pay zones atop each other (400 ft TVD apart) that were both legitimate candidates for development using horizontal wells. This discovery occurred in February of 2006 while drilling a series of 20 non-horizontal oil wells from the Kaphong Delta satellite production platform (a.k.a., KPWD) within the Kaphong Oil Field. The problem, however, at the time of this discovery is that only one of the 20 available drilling slots was still undrilled; thus, forcing a difficult choice to be made. Do we stay within our presently well-defined technology knowledge envelope and drill a single horizontal well bore, leaving one of the two producing horizons fallow until it can be drilled at a later date from an abandoned drilling slot? Or, do we step slightly beyond our local experience base and attempt drilling a multilateral well bore so as to immediately maximize the oil rate potential presented by these two producing horizons? Given ample time, all the necessary engineering steps for making this decision can be performed to arrive at a logical and well-defined solution. In this instance, however, time was not abundant. From the time it was understood that two economically viable horizontal well targets existed, only 5 weeks remained before the drilling rig must either spud this well or move to another platform. This, in turn, compressed the time window for deciding how to proceed with this project to only two weeks, allowing the balance of time for appropriate pre-drill engineering and operational planning.

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