Abstract
The hydraulic refracturing operations are often used to improve oil deliverability in the low-permeability reservoir. When the development of oilfields has entered a high water cut stage, oil deliverability can be promoted by refracturing reservoirs. The orientation of the new fracture formed by refracturing will be changed. The new formed fracture is called reorientation fracture. To calculate the oil deliverability of the refracture wells, a three-section fracture which includes reorientation fracture was established. The multiwell pressure drop superposition theory is used to derive the analytical solution of the refracture wells which includes the reorientation fracture. The numerical simulation was conducted to validate the results of the analytical solution. Comparing the refracture well deliverability of reorientation and nonreorientation, permeability, deflection angle, and the length of reorientation fracture will jointly control the productivity of refracture well. When the permeability in the direction of maximum principal stress is greater than the permeability in the direction of minimum principal stress, the capacity of reorientation fractures is relatively large. The deflection angles and the length of the reorientation fracture will directly affect the drainage area of the fracture, thus affecting productivity. The reorientation fractures generated by repeated fracturing have great potential for improving oil deliverability in the anisotropic low-permeability reservoirs.
Highlights
The hydraulic fracturing or refracture operations have been widely used to improve oil deliverability in developing lowpermeability reservoirs
Refracture can be created in two forms: one form is that the directions of the new fracture propagate the same as the original fracture, and the other is that the directions of the new fracture propagate to a new direction with the redistribution of pressure
The model used multiwell pressure drop superposition principle to calculate integral for the oil productivity formulation of the reorientation fracture, which is validated by using reservoir numerical simulation and comparing the productivity of the nonreorientation fracture
Summary
The hydraulic fracturing or refracture operations have been widely used to improve oil deliverability in developing lowpermeability reservoirs. Compared to drill new wells, refracture operations have been an economical way for improving oil deliverability [6,7,8,9]. The generation of hydraulic fracturing fractures creates favorable conditions for the development of low permeability reservoirs [27,28,29,30]. A mathematical model to describe the oil deliverability of a reorientation fracture in anisotropic low-permeability hydrocarbon reservoirs was proposed in this paper. The model used multiwell pressure drop superposition principle to calculate integral for the oil productivity formulation of the reorientation fracture, which is validated by using reservoir numerical simulation and comparing the productivity of the nonreorientation fracture. It is proved that the productivity of the diverting fracture in different anisotropic low-permeability is controlled by the anisotropy of reservoir permeability, the length of reorientation fracture, and the angle between the reorientation fracture and the original fracture
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