How to Decide Between Horizontal Transverse, Horizontal Longitudinal and Vertical Fractured Completion

Abstract

Augmented by the recent activities in shale gas, hydraulic fracturing of horizontal wells has become increasingly popular, although the technology has existed for over 20 years. The success in shale gas activities and advances in completion technology may have generated the false impression that fractured horizontal wells may be successfully applied to almost any formation.Although the very low-permeability shale gas formations in the cost-controlled environment of North America may have justifiably made multiple-fractured horizontal wells the completion of choice, many do not realize that there are circumstances where a simple vertical fractured well may significantly outperform a fractured horizontal well. Because it is usually too late to change completion type once the wellbore has been drilled, it is vital that the selection of type of fractured completion to be used is considered during initial well and field development planning. This paper will discuss the production mechanisms from horizontal transverse, horizontal longitudinal and vertical fractured wellbores. Calculations of the incremental performance of each configuration are done for both oil and gas wells. There are physical and economic limits and criteria. For example, for gas wells in reservoirs above 0.5 md, there is an unacceptable reduction in the performance of each transverse fracture because of enhanced turbulence effects. There are also economic criteria for selecting which type of completion is the optimum choice. We look at a range of reservoir and proppant pack permeabilities and discuss the optimization of fracture geometry. The paper not only delineates areas of indicated application of each well completion but it highlights the importance of considering the hydraulic fracturing process from the very start of wellbore planning. The processes involved in planning a wellbore for efficient decision making and maximum flexibility of choice are also described. IntroductionFractured well performance has been an essential element in production optimization and, obviously, this type of well completion has been a very successful petroleum engineering exercise spanning six decades. In particular over the past 15 years fracturing has grown to be the second largest upstream petroleum industry investment, right after drilling.The fracturing process is primarily aimed at well stimulation, but it provides other benefits as well. These include sand production control, connection of layered and laminated formations by vertical penetration, and in the case of gas wells, the considerable reduction of turbulence effects that dominate well performance in reservoirs with moderate to high permeability (Economides and Martin, 2007.) In addition, fracturing affords the ability to spread depletion deep into the reservoir, thus significantly increasing economically recoverable reserves, especially in gas reservoirs.To complicate things and, especially the decision-making of well geometry, about 20 years ago, horizontal wells became targets of hydraulic fractur...

Actual and Optimal Hydraulic-Fracture Design in a Tight Gas Reservoir

“…Relationships in Ehlig- Economides (1992) showed that post-treatment pressure-buildup transients in very-low-permeability reservoirs are dominated by the hydraulicfracture behavior and will not provide a straightforward permeability estimation on the basis of radial flow in a reasonable shutin time. Furthermore, when the fracture length approaches the drainage length, post-fracture radial flow will never appear, even in long-term production data, and Economides et al (2013) show that permeability estimation requires assumptions about the fracture length and/or conductivity.…”

A Study of Transversely vs Longitudinally Fractured Horizontal Wells in a Moderate-Permeability Gas Reservoir

“…For gas production there is a need to adjust the fracture design to account for non-Darcy flow, especially for transverse hydraulic fractures created in horizontal wells. Economides and Martin (2010), indicated that vertical wells with vertical fractures outperform multiple transverse fractures in horizontal wells for permeability above 0.5 md. However, another possibility would be to create longitudinal fractures from horizontal wells drilled in the direction normal to minimum stress.…”

Controlling the Height of Multiple Hydraulic Fractures in Layered Media

“…Several resources in reservoir-engineering literature suggest guidelines for choosing the optimal fracture dimensions, fracture spacing, and number of fractures for a given set of reservoir parameters (e.g., Mukherjee and Economides 1991;Economides et al 2002;Wei and Economides 2005;Meyer et al 2010;Bhattacharya and Nikolaou 2011). These studies are invariably based on the assumption that the fractures are primarily contained within the pay zone and use the Perkins-Kern-Nordgren-type fracture geometries in their calculations (Bunger et al 2013).…”