Horizontal wells have become the "industry standard" for unconventional and tight formation gas reservoirs. Because these reservoirs have poorer quality pay it takes a good well planned completion and fracture stimulation(s) to make an economic well. Even in a sweet spot in the unconventional and tight gas reservoir good completion and stimulation practices are required otherwise a marginal or uneconomic well results. But what are good completion and stimulation practices in horizontal wells? What are the objectives of horizontal wells and how do we relate the completion and stimulation(s) to achieving these goals? How many completions/stimulations do we need for best well performance and/or economics? How do we maximize the value from horizontal wells? When should a horizontal well be drilled longitudinally or transverse? These are just a few questions to be addressed in the subsequent paragraphs.
This paper focuses on some of the key elements of well completions and stimulation practices as they apply to horizontal wells. Optimization studies will be shown and used to highlight the importance of lateral length, number of fractures, inter-fracture distance, fracture half-length, and fracture conductivity. These results will be used to discuss the various completion choices such as cased and cemented, open hole with external casing packers, and open hole "pump and pray" techniques. This paper will also address key risks to horizontal wells and develop risk mitigation strategies so that project economics can be maximized. In addition, a field case study will be shown to illustrate the application of these design, optimization, and risk mitigation strategies for horizontal wells in tight and unconventional gas reservoirs.
This work provides insight for the completion and stimulation design engineers by:
Developing well performance and economic objectives for horizontal wells and highlighting the incremental benefits of various completion and stimulation strategies,
Establishing well performance and economic based criteria for drilling longitudinal or transverse horizontal wells,
Integrating the reservoir objectives and geomechanic limitations into a horizontal well completion and stimulation strategy,
Identifying horizontal well completion and stimulation risks and risk mitigation strategies for pre-horizontal well planning purposes.
For many years operators have utilized hydraulic fracturing to improve the performance of vertical, deviated, and horizontal wells. Although often successful, these operators have reported more difficulty fracture stimulating deviated and horizontal wells than occurred during the stimulation of vertical wells in the area. Generally, the difficulties fracture stimulating deviated and horizontal wells is evidenced by increased treating pressures and elevated post fracture Instantaneous Shut-In Pressures.