Abstract
Temperature is one of the most prominent factors affecting production operations, predicting the accurate wellbore-formation temperature in a water-flooding production well is of great importance for multiple applications. In this paper, an improved coupled model of oil–water two-phase fluid flow and heat transfer was developed to investigate the transient temperature behavior for a producing well with multiple pay zones. Firstly, a novel method was derived to simulate the water saturation and the water breakthrough time (WBT) for tubing, which are key monitoring parameters in the process of water flooding. Then, we incorporated water saturation and an equation set for immiscible displacement to calculate the seepage velocity and the pressure of the two-phase fluid in the pay zones. Next, the upward seepage velocity of the tubing fluid change with depth was focused on, and the proper coupled initial and boundary conditions are presented at the interfaces, therewith the implicit finite difference method was used to compute the transient temperature with the input of the seepage characteristics for the reservoirs. Meanwhile, the validity of the proposed model has been verified by the typical model. Finally, a sensitivity analysis delineated that the production rate and the production time had a significant impact on the tubing fluid temperature. The overburden was hotter with a lower volumetric heat capacity or a higher thermal conductivity. In addition, the sensitivity of the porosity and the irreducible water saturation to formation temperature was significantly different before and after the WBT. The coupled model presented herein helps to advance the transient seepage characteristics analysis of pay zones, the precise temperature prediction is very useful for reservoir characterization and production analysis purposes and provides insight for designing the exploitation scheme in deep reservoirs and geothermal resources.
Highlights
Knowing the precise wellbore-formation temperature in various kinds of producing wells is a serious challenge of great importance for multiple applications in deep reservoirs and geothermal resource exploration and exploitation
Significant advances have occurred in downhole temperature prediction since the seminal work of Ramey [9], whose landmark work addressed approximate methods to simulate the temperature of single-phase incompressible liquid and ideal gas flowing in injection or production wells
A new attempt was made by Shi et al [24], who proposed an improved numerical method to simulate the downhole temperature distribution for producing oil wells with multiple pay zones, the heat convection was highly regarded due to the fluid flow from the porous formation to the wellbore, but the fluid velocity and the saturation variation of oil–water two-phase pay zones that change with production times were ignored
Summary
Transfer to Transient Temperature Distribution and Seepage Characteristics for Water-Flooding.
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