Pressure-Transient Behavior of Horizontal Wells With Finite-Conductivity Vertical Fractures
- L. Larsen (Rogaland Research Inst.) | T.M. Hegre (Restek A/S)
- Document ID
- Society of Petroleum Engineers
- International Arctic Technology Conference, 29-31 May, Anchorage, Alaska
- Publication Date
- Document Type
- Conference Paper
- 1991. Society of Petroleum Engineers
- 5.8.6 Naturally Fractured Reservoir, 5.1.2 Faults and Fracture Characterisation, 2.2.2 Perforating, 5.6.4 Drillstem/Well Testing, 5.5 Reservoir Simulation, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation
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Methods are introduced to generate synthetic pressure-transient data for horizontal wells with finite-conductivity vertical fractures. For the main results flow from the reservoir is only assumed to take place through the fractures, but methods to include flow directly to the wellbore are also outlined. Although the paper is aimed mainly at transverse circular fractures, mathematical derivations for flow to rectangular fractures has also been included. Boundaries and multiple fractures can be treated with considerable flexibility, but examples discussed in the paper are restricted to individual or pairs of circular fractures in unbounded reservoirs, and hence also to single circular fractures in the presence of a sealing fault.
The approach taken follows classical studies of vertical wells with finite-conductivity vertical fractures. Basic solutions are developed in terms of Laplace transforms, with numerical inversion used to obtain end results. The main objective of the paper is to introduce methods to generate synthetic data for fracture horizontal wells. Application of the methods to investigate productivity of various well and fracture configurations has not been considered. Only cases to illustrate the methods are included.
The results of the paper are verified in part by comparisons with models developed for vertical wells producing layered and double-porosity reservoirs and producing layered and double-porosity reservoirs and with results fracture a 3D, finite-difference, numerical reservoir simulator.
Soliman et al. investigated the pressure-transient behavior of horizontal wells with production taking place through finite-conductivity vertical fractures. place through finite-conductivity vertical fractures. For transverse circular fractures they obtained a Laplace-transformed solution valid for the period when flow in the reservoir can be treated as linear (towards the fracture plane). Moreover to investigate effects of flow from beyond the radial real of fractures, their including was identified by extending the fracture by including an outer zone of another conductivity. Flow from the formation was still assumed to be linear.
One objective of Ref. 1 was to compare the effectiveness of finite-conductivity vertical fractures intercepting horizontal and vertical wellbores. In this comparison, strictly valid only for short flowing times (with duration depending on system parameters), a transverse circular fracture with parameters), a transverse circular fracture with diameter equal to the formation thickness was assumed. Although the present paper draws heavily on the methods used by Cinco-Ley et al. to model flow to finite-conductivity vertical fractures, direct comparisons of the two models have not been considered. Ref. 1 covers some of that ground.
The basic approach taken in this paper follows closely the approach used in Ref. 2 to model flow to finite-conductivity vertical fractures intercepting vertical wells, but the basic solutions are different. For the case with flow from the formation only take place that a single circular fracture with inner place that a single circular fracture with inner radius corresponding to the wellbore of a horizontal well, solutions for radial flow and radial subdivision of the fracture are used. Also, to model flow fracture the formation to the fracture, a solution for flow to a point in an unbounded three-dimensional reservoir has point in an unbounded three-dimensional reservoir has been used in an integral setting to generate solutions for flow to uniform-flux circular and rectangular fractures in similar used reservoirs. All these results are developed in terms of Laplace transforms, with the Stehfest algorithm used to invert the transformed solutions. For rectangular fractures following the wellbore, a somewhat simplified model has been outlined.
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