Use of a New Thermodynamics-Based Saturation/Pressure Relationship in Two-Phase Rate-Transient Analysis of Boundary-Dominated Gas/Condensate Reservoirs

SPE Journal ◽  
2020 ◽  
Vol 25 (04) ◽  
pp. 1636-1656
Author(s):  
Qian Sun ◽  
Luis F. Ayala
Keyword(s):  
Case Studies ◽  
Transient Analysis ◽  
Saturation Pressure ◽  
Gas Condensate ◽  
Production Data ◽  
Volume Depletion ◽  
Two Phase ◽  
Gas Condensate Reservoirs ◽  
Steady State Method ◽  
Rate Transient Analysis

Summary Considerable research has been focused on the development of rate-transient-analysis (RTA) models to estimate the reserves of gas/condensate reservoirs. Currently, broadly deployed RTA tools rely on multiphase pseudopressure concepts to enable multiphase production-data analysis. In any multiphase pseudopressure calculation, the determination of the saturation/pressure (So/p) relationship plays a vital role because it directly influences the ability of multiphase RTA methods to reliably forecast original gas in place (OGIP). In this work, we present a thermodynamics-based So/p model that provides a better understanding of the phase behavior for the boundary-dominated gas/condensate reservoirs. The proposed So/p model is derived from the thermodynamic nature of extended black-oil formulations. A noniterative flash-calculation protocol is used to establish the So/p path in the condensate-buildup region. The developed method can be coupled with RTA tools and services for the calculation of multiphase pseudopressure. In this work, we present case studies of three gas/condensate reservoirs with different types of fluids. Two RTA multiphase analysis models are used to scrutinize the production data using the newly proposed So/p relationship, and results are compared with the use of a traditional steady-state method coupled with constant-volume-depletion (CVD) data. Results of the case studies show that RTA models that use the proposed So/p consistently yield more accurate OGIP estimation. Thus, this work presents a practical approach to remove commonly used yet potentially faulty assumptions in multiphase RTA applications for liquid-rich gas/condensate reservoirs.

Analytical Rate-Transient Analysis and Production Performance of Waterflooded Fields with Delayed Injection Support

2021 ◽  
pp. 1-23
Author(s):  
Daniel O'Reilly ◽  
Manouchehr Haghighi ◽  
Mohammad Sayyafzadeh ◽  
Matthew Flett
Keyword(s):  
Steady State ◽  
Transient Analysis ◽  
Water Injection ◽  
Data Interpretation ◽  
Production Performance ◽  
Production Data ◽  
Reservoir Properties ◽  
Two Phase ◽  
Production Forecasting ◽  
Rate Transient Analysis

Summary An approach to the analysis of production data from waterflooded oil fields is proposed in this paper. The method builds on the established techniques of rate-transient analysis (RTA) and extends the analysis period to include the transient- and steady-state effects caused by a water-injection well. This includes the initial rate transient during primary production, the depletion period of boundary-dominated flow (BDF), a transient period after injection starts and diffuses across the reservoir, and the steady-state production that follows. RTA will be applied to immiscible displacement using a graph that can be used to ascertain reservoir properties and evaluate performance aspects of the waterflood. The developed solutions can also be used for accurate and rapid forecasting of all production transience and boundary-dominated behavior at all stages of field life. Rigorous solutions are derived for the transient unit mobility displacement of a reservoir fluid, and for both constant-rate-injection and constant-pressure-injection after a period of reservoir depletion. A simple treatment of two-phase flow is given to extend this to the water/oil-displacement problem. The solutions are analytical and are validated using reservoir simulation and applied to field cases. Individual wells or total fields can be studied with this technique; several examples of both will be given. Practical cases are given for use of the new theory. The equations can be applied to production-data interpretation, production forecasting, injection-water allocation, and for the diagnosis of waterflood-performanceproblems. Correction Note: The y-axis of Fig. 8d was corrected to "Dimensionless Decline Rate Integral, qDdi". No other content was changed.

Modeling Two-Phase Flowback of Multifractured Horizontal Wells Completed in Shale

SPE Journal ◽  
2013 ◽  
Vol 18 (04) ◽  
pp. 795-812 ◽  
Author(s):  
C.R.. R. Clarkson ◽  
J.D.. D. Williams-Kovacs
Keyword(s):  
Shale Gas ◽  
Transient Analysis ◽  
Horizontal Wells ◽  
Production Data ◽  
Two Phase ◽  
Fracture Properties ◽  
Rate Transient Analysis ◽  
Wellbore Storage ◽  
Fluid Production

Summary Early fluid production and flowing pressure data gathered immediately after fracture stimulation of multifractured horizontal wells may provide an early opportunity to generate long-term forecasts in shale-gas (and other hydraulically fractured) reservoirs. These early data, which often consist of hourly (if not more frequent) monitoring of fracture/formation fluid rates, volumes, and flowing pressures, are gathered on nearly every well that is completed. Additionally, fluid compositions may be monitored to determine the extent of load fluid recovery, and chemical tracers added during stage treatments to evaluate inflow from each of the stages. There is currently debate within the industry of the usefulness of these data for determining the long-term production performance of the wells. “Rules of thumb” derived from the percentage of load-fluid recovery are often used by the industry to provide a directional indication of well performance. More-quantitative analysis of the data is rarely performed; it is likely that the multiphase-flow nature of flowback and the possibility of early data being dominated by wellbore-storage effects have deterred many analysts. In this work, the use of short-term flowback data for quantitative analysis of induced-hydraulic-fracture properties is critically evaluated. For the first time, a method for analyzing water and gas production and flowing pressures associated with the flowback of shale-gas wells, to obtain hydraulic-fracture properties, is presented. Previous attempts have focused on single-phase analysis. Examples from the Marcellus shale are analyzed. The short (less than 48 hours) flowback periods were followed by long-term pressure buildups (approximately 1 month). Gas + water production data were analyzed with analytical simulation and rate-transient analysis methods designed for analyzing multiphase coalbed-methane (CBM) data. This analogy is used because two-phase flowback is assumed to be similar to simultaneous flow of gas and water during long-term production through the fracture system of coal. One interpretation is that the early flowback data correspond to wellbore + fracture volume depletion (storage). It is assumed that fracture-storage volume is much greater than wellbore storage. This flow regime appears consistent with what is interpreted from the long-term pressure-buildup data, and from the rate-transient analysis of flowback data. Assuming further that the complex fracture network created during stimulation is confined to a region around perforation clusters in each stage, one can see that fluid-production data can be analyzed with a two-phase tank-model simulator to determine fracture permeability and drainage area, the latter being interpreted to obtain an effective (producing) fracture half-length given geometrical considerations. Total fracture half-length, derived from rate-transient analysis of online (post-cleanup) data, verifies the flowback estimates. An analytical forecasting tool that accounts for multiple sequences of post-storage linear flow, followed by late-stage boundary flow, was developed to forecast production with flowback-derived parameters, volumetric inputs, matrix permeability, completion data, and operating constraints. The preliminary forecasts are in very good agreement with online production data after several months of production. The use of flowback data to generate early production forecasts is therefore encouraging, but needs to be tested for a greater data set for this shale play and for other plays, and should not be used for reserves forecasting.

scholarly journals Maximizing the Benefit of Rate Transient Analysis for Gas Condensate Reservoirs

2021 ◽  
Vol 118 (5) ◽  
pp. 1411-1423
Author(s):  
Mahmoud Abdo Tantawy ◽  
Ahmed A. M. Elgibaly ◽  
Ahmed Mohamed Farag
Keyword(s):  
Transient Analysis ◽  
Gas Condensate ◽  
Gas Condensate Reservoirs ◽  
Rate Transient Analysis

scholarly journals Flowing Material Balance and Rate-Transient Analysis of Horizontal Wells in Under-Saturated Coal Seam Gas Reservoirs: A Case Study from the Qinshui Basin, China

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4887
Author(s):  
Suyang Zhu ◽  
Alireza Salmachi
Keyword(s):  
Transient Analysis ◽  
Horizontal Well ◽  
Material Balance ◽  
Production Data ◽  
Coal Seam Gas ◽  
Two Phase ◽  
Rate Transient Analysis ◽  
Flowing Material ◽  
Phase Water ◽  
Water Gas

Two phase flow and horizontal well completion pose additional challenges for rate-transient analysis (RTA) techniques in under-saturated coal seam gas (CSG) reservoirs. To better obtain reservoir parameters, a practical workflow for the two phase RTA technique is presented to extract reservoir information by the analysis of production data of a horizontal well in an under-saturated CSG reservoir. This workflow includes a flowing material balance (FMB) technique and an improved form of two phase (water + gas) RTA. At production stage of a horizontal well in under-saturated CSG reservoirs, a FMB technique was developed to extract original water in-place (OWIP) and horizontal permeability. This FMB technique involves the application of an appropriate productivity equation representing the relative position of the horizontal well in the drainage area. Then, two phase (water + gas) RTA of a horizontal well was also investigated by introducing the concept of the area of influence (AI), which enables the calculation of the water saturation during the transient formation linear flow. Finally, simulation and field examples are presented to validate and demonstrate the application of the proposed techniques. Simulation results indicate that the proposed FMB technique accurately predicts OWIP and coal permeability when an appropriate productivity equation is selected. The field application of the proposed methods is demonstrated by analysis of production data of a horizontal CSG well in the Qinshui Basin, China.

Rate-Transient Analysis of a Constant-Bottomhole-Pressure Multihorizontal Well Pad with a Semianalytical Single-Phase Method

SPE Journal ◽  
2020 ◽  
Vol 25 (06) ◽  
pp. 3280-3299
Author(s):  
Hongyang Chu ◽  
Xinwei Liao ◽  
Zhiming Chen ◽  
W. John John Lee
Keyword(s):  
Transient Analysis ◽  
Single Phase ◽  
Unconventional Reservoirs ◽  
Phase Method ◽  
Production Data ◽  
Transition Flow ◽  
Well Spacing ◽  
Rate Transient Analysis ◽  
Negative Effect ◽  
Bottomhole Pressure

Summary Because of readily available production data, rate-transient analysis (RTA) is an important method to predict productivity and reserves, and for reservoir and completion characterization in unconventional reservoirs. In addition, multihorizontal well pads are a common development method for unconventional reservoirs. Close well spacing between multifractured horizontal wells (MFHWs) in the multiwell pads makes interference from adjacent MFHWs especially significant. For RTA of production data from multihorizontal well pads, the influence of adjacent MFHWs cannot be ignored. In this work, we propose a semianalytic RTA model for the multihorizontal well pad with arbitrary multiple MFHW properties and starting-production times. Combining Laplace transformation and finite-difference analysis, we obtained a general solution of a multiwell mathematical model to use in RTA. Our model is applicable to cases of multiple MFHWs with different bottomhole pressures (BHPs), varying hydraulic-fracture properties, and different starting-production times. In the solutions, we observe bilinear flow, linear flow, transition flow, and multi-MFHW flow. Rate-normalized pressure (RNP) and its derivative are also affected by multi-MFHW flow. Two case studies revealed that the negative effect of interwell interference on the parent-well productivity is closely related to the pressure distribution caused by the production of child wells.

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