Conventional diverting techniques and novel fibr-assisted self-diverting system in carbonate reservoir acidizing with successful case studies

Conventional diverting techniques may not be useful, and the use of the advanced and well-documented diverting technique is needed to overcome the complexity and heterogeneity of carbonate reservoirs. Nowadays, there have been a lot of materials and techniques utilized for acid diversion. This paper aimed to consider various utilization of fiber-assisted self as the diverting system in acidifying carbonate reservoirs. One of the main reasons for its ability to overcome uncertainty is that the fiber itself is an inherent property, allowing for an automatic diversion adjustment downhole. When a media with infinite permeability, such as a perforation tunnel or natural fracture, is filled and bridged with a material of finite permeability such as degradable fiber, this creates a temporary skin to injectivity in that zone. This is a powerful concept, as it is a way, despite uncertainty from a lack of logging data or uncertainty in the data itself, of dampening the reservoir’s natural permeability contrast. It does not rely on petrophysical certainty to design a successful treatment

Analysis of refracturing activities in the major shale plays in the United States

Refracturing of existing horizontal multistage wells has increased over the past decade in the oil industry. This work aims to investigate all the refracturing operations in the most active shale plays in the united states (Bakken, Niobrara, Marcellus, Permian, Eagle Ford, Barnett, and Haynesville) in terms of completion technique, candidate selection, treatment types, and refracturing production efficiency. To collect the data of the refractured wells, an advanced data analytics approach was applied to separate the refractured wells from 170,000 wells reported in FracFocus, a public chemical registry for hydraulic fracturing in the United States, and combine it with DrillingInfo database, a database of oil and gas production in the United States. More than 1200 refractured wells (2008-2020) were identified for study across the major shale plays in the United States. Trends in completions and production of these refractured wells were identified, for example, the most common type of treatment fluid used in refractured wells was hybrid fluids. In addition, an extensive literature review was conducted to identify criteria for refract candidate selection. Using perforated length as a proxy for stage data, 39 wells of the 1200 refractured wells production were found to be sufficiently similar to be grouped for production comparisons. This analysis, coupled with individual well plots of full production histories, demonstrate that while refracturing can restore production rates significantly, the production of the refractured well commonly declines rapidly --Abstract, page iv

Applications of aerospace technology to petroleum extraction and reservoir engineering

Through contacts with the petroleum industry, the petroleum service industry, universities and government agencies, important petroleum extraction problems were identified. For each problem, areas of aerospace technology that might aid in its solution were also identified, where possible. Some of the problems were selected for further consideration. Work on these problems led to the formulation of specific concepts as candidate for development. Each concept is addressed to the solution of specific extraction problems and makes use of specific areas of aerospace technology

IDENTIFYING RESERVOIR COMPARTMENTALIZATION USING FIELD DATA – FIELD X CASE STUDY

Identifying reservoir’s compartmentalization of Field X using field data is about subdividing a reservoir into segments that behave as separate flow units during production. It is caused by barriers to fluid flow. Flow barriers can be of different strengths ,ranging from relatively minor features that may inhibit flow to major features that will not allow any fluid communication. Reservoir compartmentalization is often a key uncertainty during reservoir appraisal. It may control the spatial distributions of reserves because different compartments may contain different oil water contacts and fluids of different composition (e.g. gas-oil ratio).Ideally ,reservoir compartmentalization should be mapped during reservoir appraisal so that this knowledge can be factored into field commerciality decisions ,development planning and facility designs (e.g. number of wells needed to drain oil) . The problem is that the dynamic data so useful for identifying compartmentalization during production usually lacking at the appraisal stage. Therefore, making the best use of the data that are available during reservoir appraisal is important. The purpose of the project is to show that by integration of initial dynamic data ,it is possible to identify the reservoir compartments at an early stage in field life .Those data are : Pressure data PVT data Well test analysis Log dat

Monobore completion design: Classification, applications, benefits and limitations

A monobore completion is a simple completion design that uses the same internal diameter from the bottom of the well to surface. This may be accomplished by cementing a string of casing in a well, or by having tubing stabbed into a polished bore receptacle on a casing liner the same size as the tubing. Monobore completions have been applied extensively in oil and gas fields around the world, both onshore and offshore, from very low reservoir flow to extremely high production rates, since the late 1980s. They have proven beneficial due to their simplicity and cost savings. This study summarizes an extensive literature review of monobore completions and categorizes the monobore completions as slimhole, big bore or special function applications. This study also evaluates the well inflow impact of the 4 1/2-in. openhole multistage sleeve monobore completion employed in the North Kuwait Jurassic Gas field for HPHT wells compared to the previous completion using 3 1/2-in. tubing and 5 1/2-in. liners. The inflow evaluation was made for both volatile oil and gas condensate fluids found in this reservoir. Reservoir depletion was modeled to determine flowing life for the conventional completion versus the monobore design. The results of the modeling indicate production rate for the volatile oil case is the same in both completion designs, conventional and monobore, while in the gas condensate case the production rate is slightly higher for the monobore completion. As the monobore completion is larger, it reaches an unstable flow condition more quickly than the conventional design. However the multistage completion methodology allows all zones to be stimulated and contribute to flow, and can be equipped with a velocity string to sustain flow --Abstract, page iii

A Data Driven Approach To Optimize Re-Fracturing Operations In The Williston Basin

Because of the recent paradigm shift focusing heavily on cost minimization, many operators are now re-developing existing assets at much lower costs instead of developing newly drilled wells. Although it may seem that the hydraulic fracturing process on a well would be easier after initial stimulation, this is not usually the case and is often more difficult. Being able to identify high margin effects of treatment parameters will help engineers design hydraulic fracturing treatments to minimize average STP (STP) and minimize costs. This research develops a feature engineered multivariate regression model that identifies several high margin areas for STP reduction. These models also yield error around 2% when predicting average STP. Using the marginal effects estimated in this study, operators can start to consider minimizing STP as a design parameter that has implications for pump time, pump maintenance costs, fuel costs, and emissions

Reservoir Simulation of the Volve Oil field using AI-based Top-Down Modeling Approach

With the rise of high-performance computers, numerical reservoir simulators became popular among engineers to evaluate reservoirs and develop the fields. However, this technology is still unable to fully model the reservoirs with commingled production and highly complex geology, especially when it comes to uncertainty qualification and sensitivity analysis where hundreds of runs are required. This dissertation aims to provide a successful case study of the history matching of a complex reservoir in the North Sea (Volve field). The proposed model relies only on the measured field variables such as well, formation, completion characteristics, production rates, and operational conditions while it stays away from interpretation and assumption. More than eight years of data from the Volve field was used to generate a comprehensive dataset, and then key parameters were extracted using fuzzy pattern recognition. A system of fully coupled artificial neural networks (feed-forward and LSTM networks) was used to train, calibrate and validate the model. The Artificial neural network enables us to extract hidden patterns in the field by learning from historical data. The model successfully history-matched the well-head pressure, well-head temperature, and production rates of all the wells through a completely automated process. The forecasting capability of the model has been verified through blind validation in time and space using data that the model has not seen before. In contrast to the numerical simulator, which is only a reservoir model, this technology is a coupled reservoir and well-bore model which is able to learn the fluid motion behavior in a complex porous media with fewer resources and higher speed. The efficiency of this approach makes it a suitable tool for uncertainty quantification when a large number of runs is required. The combination of artificial intelligence and domain expertise makes this technology more reliable and closer to reality by staying loyal to field measurements

A CFD and experimental approach for simulating the coupled flow dynamics of near wellbore and reservoir

The modeling of simultaneous flow behavior through a reservoir and wellbore is important and an integrated model is needed which accounts for the transient multiphase flow in the wellbore and its surrounding region. In addition, reservoir and wellbore interface modeling and cost-effective Computational Fluid Dynamics (CFD) methodology are required to simulate the flow behavior in that region. The study outlines the development of an experimental prototype to study multiphase flow in the near wellbore region. To the best of my knowledge, this facility has the capability to accommodate a larger length scale compared to similar facilities available in the research organizations. This experimental setup can be used for investigating a wide variety of multiphase flow problems which have been considered in the present research. A CFD methodology has been developed using the 3D Navier-Stokes equations to simulate an integrated wellbore-reservoir flow. The CFD methodology has been verified for the fluid flow mechanism at near wellbore. The simulation results have been compared to the analytical solutions. Then, this model is extended to establish a coupled wellbore-reservoir framework which is based on 3D Navier-Stokes equations. The simulations have been performed to validate the newly developed CFD algorithm and various scenarios of a reservoir have been taken into consideration. The same process has been applied to investigate flow through a perforated tunnel and a new method of perforation has been discussed. The study indicates standard CFD techniques use a “numerical approach” such as the volume of fluid accounts for capillary pressure and surface tension force needs to be improved for more understanding of the flow through porous media. In this regards, Allen-Chan phase-field method has been combined with the Navier-Stokes equations to simulate multiphase flow in porous media. The simulations performed with the phase-field method have been verified with the experimental data. The experimental and CFD approach of this thesis make a unique contribution in the field of the petroleum industry and multiphase flow in porous media

Comparison of Crushed-Zone Skin Factor for Cased and Perforated Wells Calculated with and without including a Tip-Crushed Zone Effect

A number of different factors can affect flow performance in perforated completions, such as perforation density, perforation damage, and tunnel geometry. In perforation damage, any compaction at the perforation tunnels will lead to reduced permeability, more significant pressure drop, and lower productivity of the reservoir. The reduced permeability of the crushed zone around the perforation can be formulated as a crushed-zone skin factor. For reservoir flow, earlier research studies show how crushed (compacted) zones cause heightened resistance in radially converging vertical and horizontal flow entering perforations. However, the effects related to crushed zones on the total skin factor are still a moot point, especially for horizontal flows in perforations. Therefore, the present study will look into the varied effects occurring in the crushed zone in relation to the vertical and horizontal flows. The experimental test was carried out using a geotechnical radial flow set-up to measure the differential pressure in the perforation tunnel with a crushed zone. Computational fluid dynamics (CFD) software was used for simulating pressure gradient in a cylindrical perforation tunnel. The single-phase water was radially injected into the core sample with the same flow boundary conditions in the experimental and numerical procedures. In this work, two crushed zone configuration scenarios were applied in conjunction with different perforation parameters, perforation length, crushed zone radius, and crushed zone permeability. In the initial scenario, the crushed zone is assumed to be located at the perforation tunnel’s side only, while in the second scenario, the crushed zone is assumed to be located at a side and the tip of perforation (a tip-crushed zone). The simulated results indicate a good comparison with regard to the two scenarios’ pressure gradients. Furthermore, the simulations’ comparison reveals another pressure drop caused by the tip crushed zone related to the horizontal or plane flow in the perforations. The differences between the two simulations’ results show that currently available models for estimating the skin factor for vertical perforated completions need to be improved based on which of the two cases is closer to reality. This study has presented a better understanding of crushed zone characteristics by employing a different approach to the composition and shape of the crushed zone and permeability reduction levels for the crushed zone in the axial direction of the perforation

Physics-Based Forward Modeling of Multistage Hydraulic Fracturing in Unconventional Plays

This dissertation proposes a workflow for modeling of multistage hydraulic fracturing stimulation in unconventional formations. Based on the field case of a horizontal well targeted lower Wolfcamp formation in Midland Basin, this study identifies main gaps of publicly available data and provides estimations for critically important inputs: elastic properties, horizontal stress anisotropy, and pressure dependent leakoff. Breakdown and shut-in pressure are used to constrain horizontal stress anisotropy to a narrow range of 7.6-11.0% and avoid misleading published data for the Midland Basin. The developed model shows that oilfield operators can significantly, up to two times, reduce the size of the pad and associated cost without risk of streenout. From the estimation of friction losses and modeling in planar-3D model this work shows how to overcome adverse effects of stress shadowing by perforation redesign and reduce cluster spacing. Finally, fracture conductivity and production history are used to model fluid flow in two reservoir simulators. History match demonstrates that effective permeability should be several orders of magnitude higher than measured from the pressure pulse decay method. This dissertation will be useful for completion and reservoir engineers.Even though theories of fracture growth in elastic medium are known for decades, multiple field observations show limitations in their predictive power. Therefore operators tend to use descriptive, data-driven models, to further optimize completion design. This dissertation identifies gaps and misconceptions in hydraulic fracturing design and shows both the benefits and limitations of grid-based fracturing models. More importantly, it demonstrates a workflow for fracture modeling based on a limited amount of publicly available data and practical recommendations for completion redesign coming from observation from physics-driven modeling. This dissertation will be useful for completion engineers and geomechanical lab scientists