Cost-effective development of unconventional gas resources depends upon strategic application of advancing technologies. By employing efficient fracturing techniques with an appropriate multi-stage fracturing completion, operators can achieve higher initial gas rates, increased recovery rates and reduced completion costs. The completion process employs a single-trip multi-stage isolation completion system which is driving the cost-effective exploitation of difficult reservoirs. Operational issues, case studies and system improvements, such as the means to isolate water producing zones, will be covered.Key factors to be reviewed include reserve estimates, selection of number of fractures, production behavior analysis, production forecast analysis, risk analysis, fracture design, and economic evaluation.Installation strategy issues will be addressed regarding equipment and operations such as quantity and spacing of packers and sleeves as well as the fracturing process. These strategies are critical relative to achieving mechanical, volumetric and economic success which is established by the efficiency of each fracture and total gas production rate when compared to initial evaluations.The one-trip multi-stage isolation fracturing completion process reduces rig time and cost for hydraulic fracturing services, accelerates production and improves reservoir drainage. When coupled with effective fracturing strategies and best practice procedures, the system provides improved production from unconventional gas formations.
Unconventional FormationsGrowing energy demand coupled with higher depletion rates of existing reserves compared to new discoveries are creating a unwanted supply/demand gap. This gap has driven the need to increase focus on exploration and development of unconventional resources of gas. A large percentage of the world's future energy demands will be fulfilled by unconventional gas resources, with the greatest interest being in tight gas fields. The so-called unconventional natural gases are tight gas, coalbed methane (CBM), shale gas, deep earth gas, geo-pressured gas and methane hydrates (Zahid 2007). In terms of the distribution, North America, the Former Soviet Union and Centrally Planned Asia and China have large resources for CBM, shale gas, and tight sand gas. As for methane hydrate, North America, Latin, America, and the Former Soviet Union have immense resources (Kawata 2001). To produce these resources economically and efficiently, well stimulation plays a major role in achieving the optimal target production form these reservoirs. Unconventional gas reservoirs require the formation to be fractured by hydraulic means to improve the formation productivity by providing a conductive path and joining the existing fractures and cleats in the reservoir (Zahid 2007).Typical problems associated with these types of reservoirs are low permeability and reservoir compartmentalization for tight gas and shale gas and for coalbeds and the finding of suitable permeable coals that contain a large volume of sorb...