Impact of Staggered Fracture Placement on Field Development of Unconventional Gas Reservoirs: a Critical Evaluation of Overlapping SRV's

Abstract

Making optimal well spacing decisions in unconventional plays is critical for commercial viability. Given the huge areal extent of these plays and low permeability, a large number of wells are needed to optimally extract the resource. The well spacing decision has to incorporate changes in geology/reservoir characteristics, completion methodology, presence of offset wells, and economic constraints. This work shows the impact of changes in reservoir properties such as permeability, completion properties as fracture spacing and completion footprint or the areal configuration of the stimulated reservoir volume (SRV) in determining optimal well spacing. As additional development or infill wells are drilled in a section, the possibility of SRV overlap increases. When the stage/cluster placement is not staggered between the neighboring wells, the created fractures may intersect resulting in SRV destruction i.e. the fracture area accessible to the neighboring wells is less than the total fracture area created in absence of SRV overlap. With staggered placement of stages, the created fractures are at an offset and the SRV's overlap without the fractures intersecting. This results in accelerated depletion of the region between the wells by reducing the rock volume each hydraulic fracture has to drain. Thus, the neighboring wells rob some late life production potential by draining the reservoir within the study well drainage volume. The impact of the percentage of fracture overlap, fracture spacing, and reservoir permeability on overall recovery and economic value is evaluated using synthetic models. For the scenario of SRV destruction, the NPV decreased with increasing SRV overlap. With staggered placement of fractures, there is a minor loss in NPV for less than 50% SRV overlap under the economic constraints considered. Higher than 50% overlaps may be detrimental depending on permeability and fracture spacing. Changes in cost/economic constraints also impact optimal well spacing. The presented results will assist operators in planning closer well spacing by optimizing capital expenditures and hydrocarbon recovery.

What Factors Control Shale-Gas Production and Production-Decline Trend in Fractured Systems: A Comprehensive Analysis and Investigation

“…The observations of fracture complexity have led to the introduction of Stimulated Reservoir Volume (SRV), which is used to describe the shape and size of a fracture network created by hydraulic fracturing in lowpermeability reservoirs. SRV is considered as an important parameter for well performance in low permeability reservoirs because their productivity depends primarily on enhanced permeability of the SRV and the reservoir area contacted by the SRV (Jackson et al 2013;Palmer et al 2014;Suliman et al 2013).…”

Development of Shale Gas Prediction Models for Long-Term Production and Economics Based on Early Production Data in Barnett Reservoir

“…The performance prediction models are useful for predicting the EUR of a shale gas well, hence production potential of a specific area can be estimated. The EUR and production potential information are useful in field development planning stage; how many wells are drilled and when and where the wells need to be drilled [35][36][37][38][39].…”

Evaluating the Benefits of Zipper Fracs in Unconventional Reservoirs

“…For staggered, overlapping fractures, Sahai et al (2013) reports that, because of the stimulated reservoir volume's (SRV's) competency, a maximum of 50% overlapping can help ensure a positive net-present value (NPV). For staggered and overlapping fractures, another issue to consider is well interference, as reported by Mayerhofer et al (2005).…”