Estimation of Optimal Frac Design Parameters for Asymmetric Hydraulic Fractures as a Result of Interacting Hydraulic and Natural Fractures - Application to the Eagle Ford

Abstract

Estimation of permeability in the Stimulated Reservoir Volume (SRV) is a vital input in any completion optimization workflow. One method to estimate the stimulated permeability in the SRV is to couple geomechanical modeling of the interaction between hydraulic and natural fractures with hydraulic fracture mechanics commonly used to design frac jobs. The proposed approach starts by deriving strain resulting from the integration of geological, geophysical and geomechanical modeling of interacting hydraulic and natural fractures. A unique feature of this approach is its ability to predict microseismicity, thus confirming the validity of the input natural fracture model and the geomechanical approach used to evaluate its interaction with the hydraulic fractures. The optimum validated geomechanical asymmetric half-lengths are then estimated from the derived strain map. These estimated geomechanical half lengths are used as a constraint in a frac design model which is able to incorporate this information and optimize stage treatments according to the variable SRV. The frac design parameters then need to be adjusted in order to approximately match the geomechanical half-lengths provided by the strain map.A new analytical asymmetric frac design model is developed, validated with existing commercial frac design software, and used in this study. The new asymmetric analytical frac design model is a pseudo 3D model that accounts for the variation in height in an iterative approach along with considering the asymmetric half lengths due to the lateral stress gradients in a heterogeneous reservoir. The new asymmetric analytical frac design model was compared to existing commercial frac design software and was found to provide similar estimations of frac heights but in a fraction of the time needed to run the commercial frac design software. The ability to combine these models and simultaneously solve for the optimum fracture height is provided by the constraints of the geomechanical half lengths derived from the strain map. In order to guide the engineer designing a frac job an optimum selection of the design parameters to get the target fracture geometry, this paper also presents a parametric analysis using experimental design of various fracing parameters used in our asymmetric hydraulic fracture model.In this study, the workflow was successfully applied to a complex Eagle Ford well. The frac design tool optimizes important parameters such as the injection rate, fluid viscosity, proppant type, proppant size, proppant specific gravity and leak-off coefficient in order to honor the interaction of natural and hydraulic fractures accounted for in geomechanics. The frac design model also provides vital information such as the proppant schedule to be pumped and the variation of propped length, width, and net pressure as a function of time. The results of this workflow are the fracture conductivity and proppant concentration along the fracture length and their interpolation between the stages so they can be exported to any reservoir...

Interaction between hydraulic fractures and natural fractures: current status and prospective directions

“…The HF-NF interaction study results in a permeable pre-existing NF with a fingerlike crack were shown to have substantial insignificant effect of poroelasticity on changes in injected fluid pressure in the using Green's function approach (Sarvaramini and Garagash 2016). Paryani et al (2016) also combined a pseudo 3D asymmetrical frac design with 2D strain map to analytically and numerically determine the influence of frac design parameters. The authors concluded that the most influential parameters affecting the longer side of asymmetric fracture wing are drainage area, fracture height, and reservoir permeability, while the influential parameters affecting the shorter side of asymmetric fracture wing are stress gradient, fracture height, and reservoir permeability.…”

An Efficient and Robust Method to Predict Multifractured Horizontal Well Production in Shale Oil and Gas Reservoirs

“…Therefore, the theory of probability is brought into use. The basic parameter values and their regularity of distribution are gained from a typical shale oil and gas field, taking Eagle Ford as an example [24][25][26][27]. And the Monte Carlo random sampling method is used to determine a large number of parameter combinations, with which the distribution of duration time of compound linear flow can be calculated and an analysis can be done.…”

Shale Reservoir Drainage Visualized for a Wolfcamp Well (Midland Basin, West Texas, USA)

“…The MPM is an example of a meshless method [41] as the mesh is not required for a full description of the material, it is only used for calculation purposes. The proposed MPM workflow [42,43] reduces uncertainties in fracture design and optimization through the use of half lengths derived from the validated geomechanical strain.…”