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 wellbore could be drilled to tap both reservoirs. Further complicating the
problem was that the drilling rig that discovered the horizons would be moving
to a new platform 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, 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 sizeable
production increases in the last 4 years. One key component to these production
gains is the use of horizontal wellbores. Although only 20 standalone
horizontal wells had been drilled before 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 ( separated by, 400 ft true
vertical depth (TVD) that were both legitimate candidates for development using
horizontal wells. This discovery occurred in February of 2006 while drilling a
series of 20 nonhorizontal oil wells from the Kaphong Delta satellite
production platform (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 currently well-defined technology-knowledge envelope and drill
a single-horizontal wellbore, 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 wellbore 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 2 weeks, allowing the balance of time for appropriate predrill engineering
and operational planning.
In the end, the first multilateral well in the Gulf of Thailand was
successfully drilled, completed, and put on production—but not without its
share of difficulties and missteps. Implementing a technological step forward
(even if it is a small one) is never without risk. Introducing such a step into
a new country or region can only add to the possible risks. But doing it in a
compressed time frame (though necessary in some cases) certainly introduces the
greatest risk. From project inception to final completion, the team tasked with
drilling this well understood this fact. Time limits, though, demand that
trade-offs be made between execution readiness and planning completeness, with
some of those trade-offs being unintended. The purpose of this paper is to
describe the intended and unintended trade offs that occurred, their overall
impact on the project, and how they relate to the environment in which this
project was conceived and implemented.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
24 August 2006
- Meeting paper published:
13 November 2006
- Revised manuscript received:
3 December 2007
- Manuscript approved:
14 January 2008
- Version of record:
20 June 2008
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