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Title: Quantifying the Impact of Geological Heterogeneity on Gas Recovery and Water Cresting, with Application to the Columbus Basin Gas Fields, Offshore Trinidad
Author: Sech, Richard Paul
ISNI:       0000 0001 3392 2130
Awarding Body: Imperial College London (University of London)
Current Institution: Imperial College London
Date of Award: 2007
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Numerous gas field developments worldwide have maximised profitability by utilising high productivity, large-bore horizontal completions. However, this production strategy is associated with significant risk in reservoirs with a large component of water-drive, particularly if the gas column is thin, the structural relief is small, and the reservoir is producing from only one or two wells. Rapid water influx ('cresting') can lead to early water breakthrough which effectively 'kills' the well. Predicting the time to breakthrough requires proper consideration of the interaction between reservoir properties and production strategy. We present an integrated geoscience and engineering study to quantify the impact of depositional heterogeneity on gas-water fluid flow behaviour when horizontal wells are produced at high rates in the presence of a bottom water aquifer. Gas production is simulated from a reservoir model of a single shoreface-shelf parasequence, that is conditioned to' high-resolution outcrop data. Novel surface-based modelling techniques ensure that cr\rical heterogeneities are captured without recourse to upscaling. The model is representative of gas reservoirs in the Columbus Basin, offshore Trinidad and Tobago, which are currently being developed using a small number of high rate horizontal wells. We find that an understanding of well location with respect to the spatial distribution of non-reservoir. units is critical to managing production rate and delaying water break1hrough. This is because enhanced recovery occurs when heterogeneity is suppressing cresting, rather than because production is 'outrunning' the aquifer. Furthermore, when the well is protected from water cresting, aquifer support is actually observed to improve ultimate recovery. Simulation models should possess sufficient geological detail to describe the location and 3D architecture of baffles to flow. Other aspects of the reservoir description, such as permeability contrasts between facies, are much less significant. Our results explain how material balance approaches can be interpreted to improve predictions of production performance when there is a significant risk of water cresting, or the aquifer response is modified by depositional heterogeneity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available