Combined Temperature and Pressure Data Interpretation: Applications to Characterization of Near-Wellbore Reservoir Structures
- Obinna Onyinye Duru (Stanford University) | Roland N. Horne (Stanford University)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 30 October-2 November, Denver, Colorado, USA
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 5.6.4 Drillstem/Well Testing, 5.5 Reservoir Simulation, 5.2.1 Phase Behavior and PVT Measurements, 5.1.1 Exploration, Development, Structural Geology, 5.6.3 Pressure Transient Testing, 5.2 Reservoir Fluid Dynamics, 5.1.5 Geologic Modeling, 1.6.9 Coring, Fishing, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation
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The models that describe distributed temperature behavior in a reservoir appear as advection-diffusion equations with forcing terms that include compressibility effects due to Joule-Thomson and adiabatic expansion. The model lends itself to solution techniques like Operator Splitting which decomposes a multiphysics, multiscale problem into components representing different simple physics and scales, where each component can be solved independently at each time step
using any appropriate technique for the physical process.
Unlike diffusion, advection does not destroy information and it is nonsmoothing and preserves sharp boundaries. By Method of Characteristics (MOC), a process can be estimated as it is advected downstream, from an initial data line, along characteristic paths at some characteristic velocity. This idea has useful implications on what information is carried by the advection processes that occur in a reservoir, such as heat advection.
In this paper, the results of solving the temperature model by Operator Splitting are presented. This approach utilizes the fact that temperature signatures, generated by spatial pressure changes in the reservoir due to Joule-Thomson and adiabatic expansion effects, are transported downstream in time from the initial line of generation to the wells. Along the corresponding characteristic curves, this transport is described by the characteristic velocity, and time to reach the well.
Importantly these curves are independent of the pressure model but are dependent on the convective thermal velocity.
The result is that reservoir structures that generate significant spatial pressure changes produce temperature signatures that are transported along the characteristic solution lines from the point of generation to the wells. Back calculations using the arrival times and and corresponding velocities give the location of the reservoir structures.
This technique was applied to the calculation of damaged radius, stimulated radius and inner boundaries of a multiring reservoir system, using temperature measurements and showed that near wellbore properties that are masked by wellbore storage in pressure transient analysis can be revealed by the slower moving temperature field. A proposal for new well test design to utilize this approach is also presented.
Until recently, reservoir analysis and wellbore flow studies have usually assumed isothermal conditions (except for thermal recovery processes). The temperature changes associated with fluid flow have been considered relatively negligible for any consideration in the analysis of flow behavior. However, a closer look at temperature measurements reveals that the flow is not isothermal - the temperature responds to changes in flow conditions sometimes registering changes up to 8oF.
The temperature profile is a function of the velocity of the flow, the pressure gradient in the reservoir, as well as thermal properties of the reservoir fluids and surrounding rocks. Because temperature is measured continuously but independently of pressure, it provides an additional source of constraining information about the reservoir.
|File Size||7 MB||Number of Pages||18|