Tengiz Reservoir Uncertainty Characterization and Modeling (Russian)

Peake, W.T.; Camerlo, Rion Harl; Tankersley, Terrell; Zhumagulova, Akmaral

doi:10.2118/139561-ru

Cited by 6 publications

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Probabilistic History Matching of Dual-Porosity and Dual-Permeability Korolev Model Using Three Discrete Fracture Models

Abdrakhmanova¹,

Iskakov²,

King³

et al. 2014

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Tengizchevroil (TCO) operates two giant carbonate oil fields, Tengiz and Korolev, located on the northeast shore of the Caspian Sea in Kazakhstan. Both fields are Middle Devonian to Upper Carboniferous isolated carbonate platforms. Since 1991, the fields have produced around 2B barrels of oil. As more geologic and dynamic data becomes available, an updated history match of the existing dynamic field models is required to provide more accurate simulation results for estimating reserves, optimizing production and assessing future field development opportunities. In this paper, we present a case study on the use of brown-field design of experiments (DoE) on dual-porosity and dual-permeability Korolev field simulation model. Korolev is a highly fractured reservoir, and the physics of fluid movement is mainly controlled by the fracture network. In order to capture the uncertainty in the extent of fracture region at Korolev, discrete low, mid and high fracture models were created. The history matching process was split into three separate DoE studies, one for each of the fracture models, to obtain good quality proxies. After history matching the three fracture models separately, a combined proxy was created, and the final probabilistic P10, P50, P90 models were selected from the suite of all low, mid and high fracture extent models. The history matching workflow consisted of selecting uncertainty parameters and ranges which honor geological data, identifying parameters having high impact on the history match quality, conducting brown-field DoE of historical and prediction periods, developing proxies for EUR objective functions and history match mis-match functions, and model selection. The majority of history matching effort was spent on the static well pressure match, followed by minimizing the modular dynamic test (MDT) pressures, production logging tool (PLT) profiles and water cut mis-match functions. Approaches in key areas which helped to improve the quality of Korolev history matched models will be discussed in detail. The history matching workflow with low, mid and high fracture models described in this paper is believed to be superior to approaches that use a single fracture realization with fracture porosity, fracture permeability and sigma (fracture-matrix interaction term) history match modifications within the simulator. This is because the use of three fracture realizations allows for adjustment of intrinsic fracture properties (fracture density, aperture size, fracture extent, etc.). In addition, the use of three separate DoE studies allows for more accurate proxy model development.

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Probabilistic History Matching of Dual-Porosity and Dual-Permeability Korolev Model Using Three Discrete Fracture Models

Abdrakhmanova¹,

Iskakov²,

King³

et al. 2014

All Days

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Karachaganak, Integrated Reservoir Studies on a Giant Field

et al. 2014

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Karachaganak Field, a Permo-Carboniferous carbonate platform, is a retrograde gas-condensate-oil reservoir located in the Pricaspian Basin. The field, in production since 1985, holds about 9 Bbls of oil and gas condensate and 48 Tcf of natural gas. Historically, the reservoir properties distribution has been debated because of both the complex depositional setting and the strong diagenetic overprint. These uncertainties have been assessed in the present study by analyzing and integrating the vast amount of geological and production data with the target of building a history matched reservoir model. Seismic facies analysis, integrated with analogues outcrop and core and log data, reveals different geological contexts that ranges from platform interior bedded deposits to aggrading mounds, prograding clinoforms, slopes and basin sediments. Different Depositional Regions, characterized by specific petrophysical characteristics, as estimated from core, log, Well-Tests, PLT and production data, were defined. The study, performed through an iterative process between geological and numerical models, allowed the definition of geologically meaningful interpretations of the complex dynamic behaviors. Different critical issues were better addressed by Depositional Region: quantity and magnitude of the enhanced permeability related to micro-fracturing and vugs, rock matrix permeability scale factors from plug to whole core, geological meaning and impact of sealing barriers, dolomite estimation and modeling, mound size range and modeling. A "best estimate" reference model has been thus defined and a very good history match achieved. The uncertainties of the field have been then investigated considering the achieved history match as the benchmark. Starting from the reference model the petrophysical characteristics of the different Depositional Regions have been changed far from the history matched wells at an estimated threshold distance not perturbing the history match. Low and high scenarios models were thusly defined. These represent possible alternative "end members" consistent with the geological data and still endorsed by the history match.

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Efficient Workflow for Assisted History Matching and Brownfield Design of Experiments for the Tengiz Field

Kassenov¹,

King²,

Chaudhri³

et al. 2014

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The main goal of history matching is to calibrate a reservoir model to production data and provide a model on which field development decisions can be made. Most of the history matching effort conducted in the industry is based on a single deterministic simulation model. With recent developments in probabilistic history matching techniques, faster computers, and efficient numerical algorithms, the opportunity to exploit these resources for efficient history matching workflows becomes available. In this paper we present a combined approach of assisted history matching followed by Brownfield Design of Experiment (DoE or ED) for model development for the Tengiz field. The Tengiz oilfield, located along the northeastern margin of the Caspian Sea, is the world's deepest producing supergiant oil field. The underlying simulation model of the field uses a dual-porosity, dual-permeability compositional formulation. The first step in the workflow was performing sensitivity study using one variable at a time analysis (OVAT) to reduce the number of uncertainties. This was followed by several Design of Experiments cycles to minimize the model misfit in static bottomhole pressures and MDT pressures and to modify the uncertainty ranges for the uncertain variables impacting the history match. The history match for the Tengiz field was achieved without any local modifications. The next step in the workflow was simulating the Brownfield DoE to create probabilistic reservoir models. The objective of this step was to develop multiple history matched models that generate a range of prediction outcomes. Two sets of prediction scenarios were considered: a base case which included all business plan work and a future development case. 203 DoE cases were run for each of the development scenarios. All DoE cases were used to generate proxy equations for the pressure mismatch functions (relative error and L2-norm) and cumulative oil production for the base case and the future development case. Multiple proxies were used to select probabilistic reservoir models while maintaining a good history match. The resulting probabilistic models will be used for reserves estimations, production optimization from existing infrastructure, design of future projects (ongoing drilling and expansion of an existing miscible flood), and to assess any future opportunities.

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Tengiz Reservoir Uncertainty Characterization and Modeling (Russian)

Cited by 6 publications

References 0 publications

Probabilistic History Matching of Dual-Porosity and Dual-Permeability Korolev Model Using Three Discrete Fracture Models

Probabilistic History Matching of Dual-Porosity and Dual-Permeability Korolev Model Using Three Discrete Fracture Models

Karachaganak, Integrated Reservoir Studies on a Giant Field

Efficient Workflow for Assisted History Matching and Brownfield Design of Experiments for the Tengiz Field

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