Horizontal Wells in Tight Gas Sands— A Method for Risk Management To Maximize Success

Abstract

Summary In general, successful applications of horizontal wells have been limited to high-permeability reservoirs and unconventional formations such as coal, chalk, and shale. Conversely, few tight-gas-sandstone reservoirs that require stimulation have realized sustained success with horizontal completions. One example of such success is the Cleveland Sand of north Texas and the Oklahoma Panhandle. Very recently, some success with horizontals has been observed in the Bossier and Cotton Valley Sands of East Texas and north Louisiana. Horizontal wells are commonly two to four times more expensive to drill and complete than offset vertical wells, yet they are theoretically capable of up to three to five times the production. Higher gas prices have lead to potentially better economics for horizontal wells (Mulder et al. 1992). However, research shows that in practice, many of these wells typically produce only 10 to 30% more than offset vertical wells. With costs more than double those of vertical wells, the economics is obviously unfavorable. This paper discusses ways to identify and manage risks when planning, drilling, and completing horizontal wells in tight-sandstone formations to improve success. Evidence has shown that shortcuts and blanket approaches do not work usually in these completion environments. A multitude of lithological and depletion possibilities exist as risks that need to be identified and managed through appropriate application of integrated drilling and completion technologies. Each risk may require different drilling and completion considerations in order to succeed. There is simply no recipe for repeat success. A detailed method is presented to identify, understand, and manage risk associated with horizontal wells drilled in tight-gas-sandstone reservoirs. The method will address all of the complex subjects that need to be considered for the successful placement and completion of a horizontal well, including reservoir description (both static and dynamic), well design, drilling, stimulation, and production. It will also illustrate consequences of what may happen if these issues are not considered properly. Through this method, horizontal-well feasibility and economic results can be determined. If a horizontal well has been determined to be viable economically, this method can consistently provide a solution as to what the best completion type (vertical or horizontal) is to recover reserves and enhance recovery efficiency in tight-gas-sandstone reservoirs.

Reducing Exploration and Appraisal Risk in Low-Permeability Reservoirs Using Microseismic Fracture Mapping

“…Although it is difficult to quantify how much the lea (Baihly et al 2009;Cipolla et al 2010;Daniels et al 2007;Fisher et al 2002 and2004;King 2010;Le Calvez et al 2007;Mayerhofer et al 2005;Mayerhofer et al 2006;Mayerhofer et al 2008;Peterman et al 2005;Vincent 2009;Waters et al 2009;Warpinski et al 2005;Warpinski et al 2008;Warpinski 2009) . Therefore, using well-pairs to enable cost-effective MSM may require slightly more wells to reliably assess a low-permeability resource.…”

“…The combination of hydraulic fracture stimulation and horizontal drilling has enabled exploitation of vast North American shale gas resources (Arthur et al 2008;Jenkins and Boyer 2008) and improved the economics of developing some tight gas resources (Baihly et al 2009). Contacting a large reservoir surface area significantly increases hydrocarbon production rates and recovery.…”

An Overview of Geomechanical Engineering Aspects of Tight Gas Sand Developments

“…Not all hydraulic fractures in the multistage treatments are successful, though increasing the number of fractures and appropriate planning increases the chances of improved production (Baihly et al, 2009). A number of openhole completion systems are available which can isolate and hydraulically fracture up to 24 separate depth intervals.…”

Appraising Unconventional Resource Plays: Separating Reservoir Quality from Completion Effectiveness

“…In recent years the application of horizontal drilling has dominated unconventional reservoir development, accessing much more reservoir volume than vertical wells and reducing the number of wells required to develop the resource. The combination of multi-stage hydraulic fracture stimulation and horizontal drilling has enabled exploitation of vast North American shale resources (Arthur et al 2008;Jenkins and Boyer 2008) and improved the economics of developing some tight gas resources (Baihly et al 2009). However, the application of horizontal drilling and the need to perform multiple hydraulic fracture treatments adds to the complexity of the completion and results in much more uncertainty when evaluating well performance and optimizing stimulation designs and completion strategies.…”