Falloff Testing Under Multiphase Flow Conditions in Naturally Fractured Reservoirs
- A. Dastan (Chevron Corporation) | M. M. Kamal (Chevron Corporation) | Y. Hwang (Texas A&M University) | F. Suleen (Chevron Corporation) | S. Morsy (Chevron Corporation)
- Document ID
- Society of Petroleum Engineers
- SPE Western Regional Meeting, 22-26 April, Garden Grove, California, USA
- Publication Date
- Document Type
- Conference Paper
- 2018. Society of Petroleum Engineers
- 5.6.3 Pressure Transient Testing, 5.6 Formation Evaluation & Management, 5.3.2 Multiphase Flow, 5 Reservoir Desciption & Dynamics, 5.4.1 Waterflooding, 5.5 Reservoir Simulation, 5.3 Reservoir Fluid Dynamics, 5.4 Improved and Enhanced Recovery, 5.8.6 Naturally Fractured Reservoir, 5.8 Unconventional and Complex Reservoirs
- Fallloff Test, Multi Bank, Natural Fractures, Dual Porosity, Multiphase
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Naturally fractured reservoirs constitute a significant portion of oil and gas fields worldwide. Like all reservoirs, waterflooding is routinely used in naturally fractured formations to increase recovery. However, the benefits of waterflooding can be limited due to early water breakthrough via the fractures. Therefore it is imperative to closely monitor the flood progress in these reservoirs. Analyzing transient tests in water injection wells, especially early in the life of the flood can provide valuable information, such as the mobilities in various regions around the well and the location of the flood front. An analytical model to design and analyze falloff transient data in naturally fractured reservoirs is highly desirable so that pressure transient analysis techniques can be applied for monitoring and optimizing secondary recovery projects.
In this paper we present a semi-analytical solution for the pressure response during falloff tests in naturally fractured reservoirs under multiphase flow conditions. We consider water injection into an oil reservoir, resulting in two-phase flow. In our model, the radial variation of fluid saturation is modeled as a multibank reservoir with constant saturation in each bank. Each bank has a different relative permeability and compressibility value, corresponding to the fluid saturation in the bank. We model naturally fractured reservoir behavior using Warren & Root's dual porosity model, which is extended to accommodate two-phase and multi-composite reservoirs. We also include capillary pressure effects in the model.
The proposed semi-analytical solution was tested and compared against numerical simulation results obtained from commercial simulators. The results have been in excellent agreement, validating our semi analytical approach. Using the proposed solution provides a rigorous and fast method to design and analyze tests. It also allows for using nonlinear regression techniques as opposed to computationally expensive trial and error matching for estimation of reservoir properties. Our analytical model can also be used as a guideline for grid refining in the vicinity of the wellbore and time-step selection in numerical simulators for transient tests analysis.
We expect our analytical method will enable operators and engineers to design and analyze falloff tests quickly and accurately in naturally fractured reservoirs.
|File Size||1 MB||Number of Pages||15|
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