Reservoir management practices are classically based on analytical models and standard Reservoir Engineering tools. In the waterfood or water alternating gas recovery process, the analysis is made traditionally with the hypothesis of constant predefined patterns. The producer – injector pair's interaction is quantified based on predefined geometrical analysis of the percentages of contribution of each injector to a producer. In the absence of certain degree of reservoir homogeneity, and also possible injection/production technical issues this method presents a lot of limitation and may lead to erroneous results. Fields in the Middle East are dominantly carbonates and the flow paths are guided by heterogeneous distribution of reservoir characteristics mainly permeability. This paper outlines a case study for the usage of streamline simulation in predefining the optimized rates of each producer and injector in order to optimize the recovery from individual pattern. The study quantified the interaction between producers and injectors pairs and defined the dynamic pattern distribution through the history. A number of attributes can be derived for each producer injector and pattern. Attributes such as the instantaneous and cumulative voidage replacement ratio, sweep efficiency and injection leakage can be analyzed in order to give more weight in the optimization stage to certain producer and certain injectors. It was concluded that the geometrical lay out of the patterns is not necessary respected and the injectors may support producers outside their geometrical patterns. There was as well a certain amount of the injection that is not contributing to any production and it is not targeting or supporting any specific well. A number of forecast scenarios were conducted and through ranking different realizations based on total patterns sweep efficiency, the best scenario was selected to determine the allowable volumes to be injected and produced. The scenario showed better control of the patterns as there was a reduction of any redundant injection and the leakage was cut down.
This paper describes accurate, efficient, and time-saving methodology for achieving the Business target by determining well allowable using advanced, integrated, and automated work-process for a gas condensate field with more than 350 (producing and injecting) well strings from a multi-layered reservoir, having varied reservoir characteristics. This paper will also illustrate challenges and enhancement opportunities toward full smart field applications. Integrated asset operation modeling (IAOM) within a digital framework provides automation to the engineering and analytical approach of allowable rate calculations. The approach comprises 3 step calculation process to determine the Well targets/allowable. Firstly, using the shareholder/reservoir management guideline along with calibrated well models for calculating the well's technical rate. Secondly, calculation of the well and reservoir available/potential rate using the well technical rates, reservoir target, and an inbuilt analytical solver. Thirdly, determination of the well allowable rate by conjugation of various well production components, including wellbore dynamics (Inflow performance and Well performance) and surface constraints. In a digital platform, this automated "Well allowable" workflow has enabled engineers and operators to determine the true potential of wells and reservoirs, thus overcoming potential challenges of computational time saving and identification of cost improvement opportunities. The use of the automated workflow has reduced the time to compute well allowable rates by more than 90% for a gas condensate field with more than 350 (producing and injecting) strings. Implementing this workflow prevented engineers from performing a tedious manual calculation on a well-by-well basis, allowing engineers to focus on engineering and analytical problems. Additionally, this efficient engineering approach provided the user with key information associated with the well's performance under various guideline indexes such as well available/potential rates, well technical rate, reservoir available rate, and rate to maintain drawdown/ minimum Bottom-hole Pressure. This advanced workflow computes the rate that can be delivered from each well corresponding to each guideline and constraint, thereby providing key inputs to various business objective scenarios for production efficiency improvement. Post-implementation, some challenges turned into opportunities to ensure the full and smooth implementation of the generated production scenarios adhering to the gas demand fluctuation. The accuracy and robustness of advanced and automated workflow of setting well allowable /production scenarios empower users to establish well performance and deliverability with a solid engineering analysis base, thereby providing key opportunities for saving cost computational time and assuring short-term production mandate deliverables. This approach supports standardization of the work process across the organization and a minimum of $ 2.8M value proposition from manpower time saving over 5 years.
This paper demonstrates the use of an integrated production optimization platform to determine the well performance for gas condensate wells in a statistical approach to increase the data accuracy for reservoir studies, simulate the field limitations, and provide recommendations for production optimization in a multilayered large carbonate reservoir field. This case involves wells under recycle and natural decline with challenges in the evaluation of well performance where the bulk of the information is available in multiple data sources The first elemental block in establishing the well performance of a gas condensate well is to determine and simulate its fluid behavior. Based on the PVT reports and subsurface fluid studies, compositional PVT models are built and matched with experimental data analyzing representative phase envelop properties and relevant Equation of State (EOS). The next step incorporates the utilization of representative physics-based well models in an integrated system to determine the reservoir and well deliverability. Finally, by applying a detailed statistical approach to the production well test history, models are calibrated in order to predict the performance of the gas condensate wells. Tuning of compositional PVT models established the EOS to be incorporated in predicting the fluid behavior and integrating representative PVT models with well models to determine such behavior along the fluid path. Using the statistical approach, the poor well measurements were identified, facilitating the well-performance and deliverability calculation. In addition, the use of representative models helped in increasing the accuracy of identifying well performance. During this study, two different methodologies were identified based on the reservoir management guidelines. Firstly, for the recycle reservoir in which, the decline of reservoir pressure is arrested using gas Injection. Secondly, for the depletion reservoir, in which the reservoir pressure declines rapidly. For the recycle reservoir, it was statistically identified that the reservoir pressure was declining at less than 4%. Therefore, the acceptance criteria for the operating envelope for each well was defined using the reservoir decline of less than 4%. Similarly, for the depletion reservoir, the pressure was declining between 7% and 10%. Thus, the operating envelope's acceptance criteria were defined using the max reservoir decline tolerance of 10%. The above-identified criteria were incorporated into the integrated model framework to validate the well performance generated from the well tests. Implementing this specialized engineering approach in an integrated model framework considerably reduces the time required by engineers to validate the production well tests and provides higher levels of accuracy for production optimization, voidage replacement ratio calculation, daily rate estimation, and surveillance.
This paper describes the implementation of the solvent model in streamline simulation and its application to WAG injection optimization for a producing field. The solvent model was implemented as an extension to the 3-component black oil model, with solvent as an additional component, to model miscible displacement process. The relative permeabilities and fluid properties of the oil and gas phases are modified based on the fraction of the solvent component, the reservoir pressure and the Todd-Longstaff mixing-parameter (i.e. an empirical treatment of the effects of physical dispersion between miscible components). The solvent model was applied to a Middle Eastern oilfield, which is currently under development using a miscible WAG process. PVT analysis has been done to prepare the properties for the reservoir gas and the injection solvent. Streamline simulation models with and without solvent model were run to compare the results with a reference finite difference compositional reservoir simulator and the effect of miscibility has been validated. Results of streamline simulation models with and without solvent model were compared against a reference finite difference reservoir simulator. The comparison shows the streamline simulation model with solvent model has much better agreement with the reference finite difference compositional reservoir simulator which shows that the miscible displacement process is properly simulated in the streamline simulation model with solvent model. The solvent model presented in this paper advances streamline simulation technology, combining the intuitive and unique properties of streamlines and the capability of simulating miscible recovery mechanism. It allows simulating both immiscible and miscible displacement within the same simulation. The solvent model considers the effects of miscibility by considering relative permeabilities and fluid properties adjustments based on pressure and solvent concentration. The technology will help effective simulation of miscible recovery process, assist optimum solvent allocation and improve unified sweep.
Objectives/Scope The development of Abu Dhabi's sour gas is not without its challenges. Deep drilling in some fields presents its own set of difficulties due to high temp and pressures coupled with +30% H2S and +10% CO2. Handling of these corrosive reservoir fluids both while drilling and then testing, requires deploying advanced technology to meet the specific requirements of these reservoirs, along with the infrastructure necessary to handle the toxic and corrosive products while testing in a brown field safely. Methods, Procedures, Process Developing local sour gas production is seen as the answer to resolve the ever growing energy needs for UAE but the technical requirements for the project is stretching the limits of the industry. Results, Observations, Conclusions What did we do different: Developed and implemented specific HSE procedures and SIMOPS due to close proximity with major populated facilities which could not be shut-down during the testing period. Conducted multiple audits and drills with the local authorities including Civil Defense and local Police. Additional 3rd part supervision was provided to ensure all personal are complying with the policy and procedures developed. Installed 2 green burners and 2 vertical 90 ft flare stacks at 180 degrees. This was to cater for the changing wind directions for continuous operations and as back ups. CCTV monitoring for green burners / flare stacks was conducted although this was a rigless operation 3 circles of H2S detectors and sensors were placed around the testing area and the flare stakes and green burners to detect any H2S gas. (Covering all 360° directions). Blowdown/Depressurization valve was installed at separator, storage tanks apart from Automatic and manual shutdown system upon H2S detection Installed Optic Fiber cable from wellhead to the main control room for monitoring purposes All piping connections used were flange-to-flange as welded joints could have caused stress cracking on the weak points For Sour well operation, used fully cladded X-mass tree & Inconel well completion Considered setting of compatible TTBP (Thru Tubing Bridge Plug) for staked reservoirs zonal isolation Instead of coil tubing cement plug for accurate depth calculations. Arranged Special chemical for any scale cleanout for handling of elemental Sulphur. Arab zones were stimulated with specialized acid recipe developed exclusively for this temperature, pressure and sour conditions downhole. Bottom hole measurements were recorded successfully and all the necessary data was acquired. Novel/Additive Information This paper highlights the major challenges identified and mitigated to test and produce the highly sour HPHT gas during the appraisal program complying with ADNOC 100% HSE in a brown field without disturbing the other major operations being performed in the vicinity.
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