Pressure Transient Analysis for Segregated Oil Water Flow
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Solution Overview
Problem
Current methods for analyzing pressure-transient tests in hydrocarbon reservoirs under segregated oil and water flow conditions are inadequate, as they are based on single-phase flow assumptions and fail to accurately determine formation flow capacity and phase mobility, particularly in giant carbonate formations where segregated flow mechanisms prevail.
Innovation Solution
A computer-implemented method and data processing system that analyzes pressure transient tests to determine oil and water flow capacities and phase mobilities by modeling the reservoir as a two-layer system, accounting for distinct properties of each phase and adjusting formation flow parameters to match test data within acceptable tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-phase flow analysis equations are used for pressure transient tests under segregated oil and water flow conditions, then the analysis can be performed using conventional methods, but the determination of formation flow capacity and phase mobility becomes inaccurate
Solution Approach 1:
The reservoir is segmented into two distinct layers: an upper oil-producing zone and a lower water-producing zone. Each layer is assigned separate flow capacity (kh) and phase mobility parameters. This segmentation allows the analysis to account for segregated flow conditions where oil and water occupy different vertical zones, enabling accurate determination of individual phase properties while maintaining analytical tractability through modified single-phase equations applied to each layer separately.
2Productivity
If the Perrine method is used to analyze multiphase flow, then pressure transient data can be interpreted, but the true formation capacity cannot be determined and reservoir characterization is limited
Solution Approach 1:
The invention extracts and separates the individual phase flow capacity parameters (kh_oil and kh_water) from the combined multiphase analysis. By applying the segmentation principle and using the relationship between water cut ratio and phase mobilities, the method extracts true formation capacity information for each phase that would otherwise be lost in conventional Perrine analysis. This extraction enables independent determination of oil and water zone properties without requiring complex numerical simulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides accurate estimates of formation flow capacity and phase mobility, improving reservoir characterization and reserve estimation by rigorously modeling segregated flow mechanisms, thereby overcoming the limitations of existing methods like the Perrine method.
Implementation Method 1
pressure transient tests can be viewed as experiments that are conducted on producing oil wells to acquire certain information about its productivity and to characterize the in-situ properties of its near-wellbore reservoir region
Implementation Method 2
In the presence of strong gravity forces in subsurface environments, having specific geometrical and petrophysical properties undergoing simultaneous flow of multiphase fluids, segregated flow mechanism of oil and water usually takes place. Under this flow mechanism, the heavier fluid, water phase in this case, tends to position itself at the lower zone of the reservoir, while the lighter fluid, oil phase, positions itself at the upper zone of the reservoir. A difference in density between the oil and water phases is the main driving force in the process of segregating the oil and the water phases.
Data Source
AI summary
A segregated flow mechanism of oil and water usually takes place in the presence of strong gravity forces in subsurface environments, having specific geometrical and petrophysical properties undergoing simultaneous flow of multiphase fluids. The segregated flow of oil and water is modeled as a two-layer reservoir system, based on the observed data. Accurate estimates or measures of the values of phase mobility of oil and water, in addition to the actual flow capacity of the formation are provided. Reliable reservoir characterizations and reserve estimations are provided based on the in-situ conditions of oil and water in the reservoir.