Abstract

As the demand for energy worldwide increases, the oil and gas industry will need to increase recovery from unconventional gas reservoirs (UGR). To economically produce UGRs, one must have adequate product price and one must use the most current technology. Tight Gas Sands (TGS) contribute three quarters to the total U.S. gas production from UGRs. TGS reservoirs require stimulation as a part of the completion, so improvement of completion practices is very important. We did a thorough literature review to extract knowledge and experience about completion and stimulation technologies used in TGS reservoirs. We developed the principal design and two modules of a computer program called Tight Gas Sand Advisor (TGS Advisor), which can be used to assist engineers in making decisions while completing and stimulating TGS reservoirs. The modules include Perforation Selection and Proppant Selection. Based on input well/reservoir parameters these subroutines provide unambiguous recommendations concerning which perforation strategy(s) and what proppant(s) are applicable for a given well. The most crucial parameters from completion best-practices analyses and consultations with experts are built into TGS Advisor's logic, which mimics human expert's decision-making process. TGS Advisor's recommended procedures for successful completions will facilitate TGS development and improve economical performance of TGS reservoirs.

Introduction

Unconventional gas reservoirs (UGR), including tight gas sands (TGS), coalbed methane, and gas shale formations, account for 40% of total U.S. gas production1 and they are expected to surpass U.S. onshore conventional reservoirs in 2009.2 TGSs contribute 76% to the total gas production from the UGRs.1 Moreover, in 2005 the U.S. Energy Information Administration estimated that TGSs could account for up to 35% of the U.S. recoverable gas resources.3 TGSs is a critical hydrocarbon source required to meet raising energy demand and its role as an energy source is constantly increasing.

The U.S. government has defined a TGS as a gas reservoir with an expected permeability of 0.1 md or less. TGSs are considered as unconventional resources, because the economic exploitation of TGSs is not feasible without advanced technologies and sophisticated stimulation treatments as a part of the completion process.

In spite of the plethora of information about development of TGSs that has been documented in the publicly available petroleum literature in the U.S.A., this knowledge is neither easily accessible nor has been systematically documented. Improved data collection and analysis including best-practices is one of the industry's most important technology challenges.4

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