Hydraulic fracture treatments are necessary to ensure the best deliverability of tight gas from east Texas Cotton Valley Sands. Historically these treatments have been performed using a wide variety of techniques using a range of fluids including slick water, linear gel, crosslinked polymers and CO2 emulsions. Most of the productive sands are associated with nearby water sands that are often intersected by the hydraulic fractures as their heights grow which results in high water production and a subsequent significant reduction in produced gas. An integrated engineering process of reservoir and production analyses was used to evaluate the stimulation treatment carried out for several offset wells throughout the field. The analyses determined the fracture geometry: fracture length, fracture conductivity, and permeability. The results were then used to calibrate a log-derived permeability and stress models. An advanced petrophysical analysis using these models improved the identification and characterization of potential movable water zones. A perforation scheme was proposed to minimize intersecting the water sands. Several stimulation techniques based on the rock mechanical model of the sands were evaluated. These included treatment with slick water, crosslinked polymer, hybrid (combination of slick water and crosslinked gel), CO2-based emulsions, and viscoelastic fluids. A high-rate hybrid treatment was selected because of the fracture geometry it would generate: bigger width, longer length, and minimal height growth.

The first new well came on production with a significantly low water-gas-ratio (WGR), from a first-year average of 483 bbl/MMscf for the offset wells to 135 bbl/MMscf for the new well. The first-year gas from this new well was more than double that of the offset wells average (163 MMscf versus 65 MMscf) and 88% higher than that of the best offset well. The polymer concentration was lowered to ensure better and earlier cleanup. On the next well drilled in the area, the same hybrid treatment was applied only to the portion of the Taylor sand located in the Cotton Valley sands. It came on line with higher gas production than the offset wells. For the first 6 months, total gas produced was 56 MMscf compared with the 40-MMscf average of the offsets, and the WGR was 147 bbl/MMscf compared with 397 bbl/MMscf.

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