Inflow Performance Relationship Models Research Articles

Revised inflow performance relationship for productivity prediction from marine sandy hydrate reservoirs in Nankai Trough

Productivity prediction is crucial for the safe and efficient exploitation of marine methane hydrate. As a feasible method, inflow performance relationship (IPR) can characterize productivity results and provide a theoretical basis for optimization of depressurization schemes. In this study, we propose two modified IPR models based on field data from limited trial production and numerical fitting in the Nankai Trough. Prediction results are obtained by depressurization, together with IPR curves under different recovery ratios. According to the conventional formulas, the reservoir pressure of the deliverability equation is revised, considering the dual contributions of hydrate dissociation and pressure drop. The comparison results show that the modified Vogel formula and Fetkovich formula can suitably describe the IPR for the single vertical well and horizontal well, respectively. Sensitivity analyses of various reservoir physical parameters indicate that changes in porosity and hydrate saturation cause diverse values for the undetermined coefficient A, primarily due to the alterations in the key coefficient pr′ in the revised Vogel formula for the vertical well scenario. However, absolute permeability has only a slight influence on the shape of the IPR curve. In contrast, absolute permeability plays a crucial role in affecting the Fetkovich-modified IPR curves for horizontal wells. Productions under varying porosities exhibit a consistent linear trend on the Fetkovich-modified IPR curve because of the comparable impact of gas production rate and pressure square variance. Besides, changing hydrate saturation can also have some effect on the IPR. Our research provides a feasible productivity prediction methodology for the safe and efficient extraction of similar hydrate reservoirs.

The inflow performance relationship in fractured, vertical, and dewatered coalbed-methane wells

Although not greatly studied, the inflow performance relationship (IPR) in dewatered and vertical coalbed methane (CBM) wells is essential in the development of a CBM reservoir. The dynamics of the stress sensitivity effect (SSE) and the matrix shrinkage effect (MSE), as well as the hydraulic fracture propagation, have all been neglected, especially for the exterior region, which is larger than the drainage radius. A novel IPR model has now been built that integrates dynamic SSE–MSE and hydraulic fracture propagation into the skin factor, and is validated with real production data from the Qinshui Basin, China. The absolute open flow rate given the SSE–MSE is 60.5% larger than without SSE–MSE. If the positive effect of the SSE–MSE on the permeability in the exterior region is neglected, the absolute open flow rate is reduced by 21%. The MSE has a greater effect on the fracturing skin factor than the SSE and tends to lower the fracturing skin factor, benefitting the production of CBM. Moreover, in light of the SSE or MSE, the non-Darcy flow effect is weaker due to restraints on the velocity of flow or the permeability. Useful and essential theoretical guidance for real CBM production can thus be gleaned from this novel IPR model.

Simplified transient-IPR modeling in intermittent gas-lift and plunger-lift systems

By solving the diffusivity equation on a periodic varying production problem, one can arrive at a transient inflow-performance relationship (IPR) model. This IPR model can then be coupled with a wellbore model to understand intermittent deliverability from wells with an artificial-lift system (ALS), such as periodic gas lift and plunger lift. The commercial simulators allowed verification of model results and field data validated the solution approach. In essence, we proposed a new alternative method to obtain the Bessel functions for the proposed transient-IPR method to minimize the undulations associated with the existing solutions.For verification of this simplified IPR modeling approach, we first attempted to replicate two-step flow rates with shut-in periods, such as those associated with a transient flow test. The model successfully reproduced those transient pressure profiles obtained from a rigorous superposition approach, generated with an analytical model. Thereafter, we replicated the results of a coupled wellbore/reservoir model for a gas-lift well, using a numerical simulator. The difference between the results of rigorous simulators and our simplified transient-IPR model turned out to be well within engineering accuracy.Field data from two plunger lift operations validated the transient-IPR model presented in this study. We observed that a smaller period of oscillation translates into a more significant error between the traditional steady-state IPR model and the actual transient-IPR model. This finding suggested the need for the accuracy of the transient-IPR model in ALS to express the realistic rates and pressures. By capturing the essence of transient behavior, we can combat downhole tool failures arising from large pressure fluctuations or issues with surface metering due to higher than expected rates.

Inflow performance relationship of vertical wells in fractured vuggy media during semi-steady state flow regime

The inflow performance relationship (IPR) is one of the essential key parameters that control the fluids production/injection rate from wells. The presence of the vugs in addition to fractures in carbonate reservoirs introduce many difficulties related the estimation of IPR of future wells. In this study, a novel analytical IPR of dual-permeability, triple porosity model is derived for the first time. The introduced IPR formula is derived for the standard scenario model of a vertical and fully penetrating well in a circular reservoir under single-phase flow of slightly compressible fluid. The three governing flow equations (matrix flow equation, fracture flow equation and interaction between vugs and other two continuum equation) are solved simultaneously as a system of differential equations for semi-steady state (SSS) flow regime. The generated SSS IPR is the same as Darcy's straight line IPR multiplied by an error parameter (E23) which is bounded between zero and one. A detailed investigation of the effect of the reservoir petro-physical parameters like storativities, inter-porosities and fracture to matrix permeability ratio are presented. The newly presented IPR of dual-permeability, triple porosity system can be reduced to sub-models IPRs by further modification of error parameter to fit sub-model as single permeability, triple porosity (E13) or dual permeability, dual porosity (E22). The presented IPR formula has the advantage of dividing the pressure drop of the fluid flow to two components, one for the internal resistance between different continuums (which is resented by E) and the other one is the radial flow in the same continuum toward/from well-bore. The generated IPR model is double verified using both cell pressure centred finite volume numerical simulation and conventional pressure transient analysis.

Study on foamy oil development effect in horizontal wells based on a novel inflow performance relationship model and a five-component model

In this paper, a novel inflow performance relationship (IPR) model and a five-component simulation model are presented for the evaluation of the foamy oil development effect in horizontal wells. First, considering the production characteristics of foamy oil including single-phase flow, foamy oil phase flow, and two-phase flow, a novel IPR model is proposed for predicting the primary production of foamy oil. Then, the five-component model is proposed to simulate the development of foamy oil. Finally, sensitivity analysis and evaluation of the development effect are conducted. The results show that (1) the novel IPR model is in good agreement with the field data, which can be used for predicting the primary production of foamy oil. (2) The five-component model is better than the four component model for simulating the foamy oil. (3) Permeability and reservoir thickness play a key role in the recovery rate of foamy oil. (4) The recovery rate of single-phase flow, foamy oil stage, and two-phase flow stage is 1.69%, 4.59%, and 4.12%, respectively. This paper provides the engineers a novel insight into the production of foamy oil in horizontal wells and also provides an optimization method of productivity evaluation for the oil field.

Transient Coupled Wellbore/Reservoir Model Using a Dynamic IPR Function

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 181691, “A Transient Coupled Wellbore/Reservoir Model Using a Dynamic IPR Function,” by A. Posenato Garcia, The University of Texas at Austin; P. Cavalcanti de Sousa, Texas A&M University; and P.J. Waltrich, SPE, Louisiana State University, prepared for the 2017 SPE Reservoir Simulation Conference, Montgomery, Texas, USA, 20–22 February. The paper has not been peer reviewed. Conventional inflow-performance-relationship (IPR) models are used in coupled wellbore/reservoir transient simulations, even if bottomhole-pressure conditions are assumed to be constant on the derivation of such IPR models. The dynamic IPR model proposed in this paper not only captures the relevant reservoir dynamics from the well perspective but also is computationally more efficient than discretized models using hundreds of gridblocks to simulate the near-wellbore region. Introduction Traditionally, well deliverability is obtained by combining IPR and vertical-flow-performance (VFP) curves. This method was first discussed in 1954 and provides snapshots of the average- bottomhole-flowing-pressure (Pwf) and average-oil-flow-rate (qo) relationships at given times in the life of the well. It fails, however, in accurately portraying the transient behavior of these variables. Transient relationships are important in the design and analysis of pressure-transient tests, design of production tubing and artificial-lift systems, reservoir management, and estimating flow rates from multiple producing zones. Capturing the real behavior of these variables requires coupling the reservoir model and wellbore model. General-use coupled models rely on running reservoir simulations (accounting for near-wellbore effects) and using the output of that run as the input to the wellbore model, which, in turn, will retrofit the reservoir simulator for a new run. This can be costly and time consuming and it is not always successful or accurate. On the other hand, coupled models developed for special cases, while still relying upon simulations, are faster and provide reliable results but have no general application. This paper introduces a new technique of coupling wellbore and reservoir models where the simulation of the reservoir response to changes in the bottomhole flowing pressure is obtained not by numerical methods but rather by solving the diffusivity equation using the Fourier transform. This mathematical tool generates time-dependent equations—the dynamic IPR—which are able to provide the reservoir response to any pressure variation, regardless of how fast or slow this change might be. Methods Conventional IPR models are algebraic equations correlating the bottomhole flowing pressure and the flow rate through the production-zone completion. Because most of these models rely on correlations and experimental-data fit, it is common practice in the industry to perform well tests periodically to correct the IPR models according to the most-updated information on the fluids and reservoir parameters. The focus of this work is on homogeneous, isotropic, circular-shaped, undersaturated oil reservoirs with a finite-diameter vertical well in the center. Thus, the authors considered IPRs that correspond to these same conditions. These IPRs are defined for three different flowing times: transient, pseudosteady state, and steady state. Please see the complete paper for the relevant equations.

Nodal Analysis for Unconventional Reservoirs—Principles and Application

Summary Nodal analysis is the standard technique used to evaluate the performance of integrated production systems. Two curves represent the capacities of the inflow and of the outflow, and the intersection of the two curves gives the solution operating point. Limitations of traditional nodal analysis include: Results are offered only at a snapshot, not as a function of time. Inflow-performance-relationship (IPR) models are limited, with none available for shale gas wells. Analysis is performed on a well-by-well basis, with no account of multiwell interference. We propose a new nodal-analysis method that enables the study of transient production systems, such as unconventional reservoirs, with IPR models generated from a high-speed semianalytical reservoir simulator and outflow curves generated from a steady-state pipeline simulator. The use of analytical reservoir simulation allows accurate, reliable modeling of the real inflow system. The new approach studies the time-lapse behavior of the system, with consideration of production history and neighboring-well interference. This new method enables the study of transient deliverability at the wellhead, where the measurement is usually available, and shows the time-lapse relationship between wellhead pressure and production rate. We provide examples of wellhead deliverability and choke management and explain advantages of the method with case studies involving tight and shale wells. The method is also applied to design and optimize artificial lift in unconventional wells and to study the method's validity over time. In addition, we discuss an example of operational well dynamics with time-lapse nodal analysis. Furthermore, this new method generates discussion about some concepts that are often taken for granted—What should be the definition of IPR in a transient production system? On the IPR curve, is the zero-rate-pressure the reservoir pressure? Can IPR curves at two different timesteps cross each other? Finding the answers to these questions will help us better understand production systems. The commonly used productivity-index (PI) method is reviewed and compared with the new method. Results show that one should not use the PI method when well operational conditions change.

Inflow performance relationships for layered solution-gas drive reservoir

Inflow performance relationship (IPR) is a very important tool to forecast well performance. Existing IPR models are idealistic since they are developed for homogeneous reservoirs; therefore, they are inappropriate for layered systems. Consequently, there is a need for IPR models that efficiently describe layered reservoir performance. This study investigates the effects of reservoir heterogeneity on IPR for layered solution-gas drive reservoirs. Multiphase flow in both two and multilayer reservoirs was simulated. Both fluid cross flow and no fluid cross flow among layers were considered. A stochastic simulation algorithm was used to generate various permeability realisations among layers. Three geostatistical models using uniform, Gaussian, and bimodal probability distributions were used to grasp optimum match between real reservoir behaviour and simulated data. The generated data were scrutinised to develop two accurate IPR equations. The first equation describes the well behaviour under current flowing conditions, whereas the second equation can be used to forecast future well performance.

New Inflow Performance Relationship for solution-gas drive oil reservoirs

Abstract The Inflow Performance Relationship (IPR) describes the behavior of the well׳s flowing pressure and production rate, which is an important tool in understanding the reservoir/well behavior and quantifying the production rate. The IPR is often required for designing well completion, optimizing well production, nodal analysis calculations, and designing artificial lift. Different IPR correlations exist today in the petroleum industry with the most commonly used models are that of Vogel׳s and Fetkovitch׳s, in addition to a few analytical correlations, that usually suffer from limited applicability. In this work, a new IPR model was developed based on actual field data for almost 50 field cases in addition to several simulated tests. This method is simple, covers wide range of reservoir parameters, easy to apply, and requires only one test point. Therefore, it provides a considerable advantage compared to the multipoint test method of Fetkovich. It also provides significant advantages over the widely used method of Vogel. (Comparison between the new method and Vogel shows that the new method is almost three times more accurate in our field tests database.) After the development of the new model, its accuracy was compared with the most common IPR models that can be computed with the readily available test and field data (Vogel, Fetkovitch, Wiggins, and Sukarno). Twelve field cases were used for comparison. The best two methods were our new model and that of Fetkovich׳s with average absolute error of 6.6% and 7%, respectively. However, the new method has the advantage of requiring only one test point as opposed to Fetknovich׳s which requires a multi-rate test. A method to compute future IPR performance was also developed and tested against field data with superior results to other available models. Finally, the application of the new model is illustrated with field examples for current and future IPR computations.

Modeling Inflow Performance Relationships for Wells Producing From Two-Layer Solution-Gas Drive Reservoirs Without Cross-Flow

Continuous monitoring and accurate anticipation of the present and future performance of the flowing wells and reservoirs constitute the cornerstone elements in the design of optimum field development strategy. It is crucial for the petroleum engineer to possess the appropriate tools that assist in efficiently predicting well behavior, designing artificial lift equipment, forecasting production, and optimizing the entire production system. Inflow performance relationship (IPR) is one of the vital tools required to monitor well performance. Existing inflow performance relationship models are idealistic and mainly designed for homogeneous reservoirs. However, most reservoirs around the world are heterogeneous and composed of layers of different permeabilities. Hence, there is an urgent need for new realistic IPR models that describe the actual reservoir inflow performance behavior more efficiently than the available models. The authors investigate the effects of reservoir heterogeneity on IPR curves for wells producing from two-layer solution-gas drive reservoirs without cross-flow. Furthermore, the results provide the petroleum engineer with two simple yet accurate IPR models for heterogeneous reservoirs. The first model represents the IPR of the well under present flowing conditions, while the second model is used to forecast future well deliverability.