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Technical Paper: Fracturing Previously Bypassed Highly Laminated Tight Gas Sands: A Production Optimization Case Study in South Texas

Society: SPE
Paper Number: 105681
Presentation Date: 2007
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Abstract

Highly laminated tight gas sand sequences remain prolific targets worldwide and have often been bypassed using standard petrophysical analysis and simple porosity cut-off technique. The problem becomes more acute in marginal tight gas reservoirs. The high cost of hydraulic fracturing increases the need for an effective and useable petrophysical model for an accurate productivity indication of the target interval. The pressure to avoid non-economical completions continues to leave hydrocarbons bypassed. Using recent advances in logging technology and production optimization modeling, the thinly laminated gas bearing permeable sands can be discerned from clay dispersed in silt and sand. A true net height can now be obtained. Through production optimization modeling, it is possible to assess the economic viability of completing and stimulating highly laminated interval. In this paper, we will show a case study from a South Texas tight gas sand field. Several wells were evaluated using micro-resistivity imaging. From this an enhanced high-resolution petrophysical analysis was created. This image-enhanced evaluation of reservoir properties was combined with production modeling. The production performance was simulated for each interval and used for recommendations on completion strategies. Additional pay intervals, normally bypassed, were perforated and hydraulically stimulated. We compared production data from offset wells that used standard petrophysical analysis to the results of the newer wells with the high-resolution analysis. The results indicated that actual field production increased and paid out the increased fracture stimulation cost. Production logs acquired across entire intervals confirmed that portions of the field produced from horizons that were previously bypassed. This process is useful for any highly laminated tight gas sand sequence and is of widespread applicability. Previously bypassed intervals can now be assessed and completed effectively and economically. This process will further add to the reserve base of tight gas.