Fracturing of High-Temperature, Naturally Fissured, Gas-Condensate Reservoirs

Abstract

Eleven hydraulic fracture treatments were performed in deep (3300 to 3800 m (10,830 to 12,470 ft)), extremely high-temperature (180 to 195{degrees}C (356 to 383{degrees}F)), naturally fissured, gas-condensate reservoirs. Formation permeabilities at the fractured-well locations range from 0.003 to 0.2 md, while the initial formation pressure gradient is about 0.13 bar/m (0.57 psi/ft). The producing fluid is high-gravity gas (0.83 to 1.15 to air) and contains up to 22% CO{sub 2} and up to 4% H{sub 2}S. Job sizes have ranged from 300 to 2000 m{sup 3} (80,000 to 528,400 gal) of fluid and 50 to 600 Mg (110,130 to 1,321,590 lbm) of high-strength proppant. This paper emphasizes the general approach to well completion and stimulation treatment design, treatment execution, and evaluation. Interesting items include the engineering of the fracturing fluids to sustain their viscosity at the extreme temperatures and to reduce leakoff in these highly fissured formations. An outline of the reservoir description is also given. Post-treatment well production has been excellent in most cases. Well PI's increased from 0.01 to 0.6 m{sup 3}/d {center dot} bar{sup 2} (0.0017 to 0.1 scf/D-psi{sup 2}) to 0.235 to 7.83 m{sup 3}/d {center dot} bar{sup 2} (0.04 to 1.3 scf/D-psi{sup 2}). Treatment resultsmore » suggest that leakoff can be controlled with particulate agents, that delayed crosslinking is the only way to execute these treatments, and that hydraulic fracturing can greatly improve the production from naturally fissured formations. Fracture design and the predicted well production are compared with post-treatment performances in selected wells.« less