This paper describe an application of combined experimental and digital technology workflow for field appraisal. It includes the description of heterogeneous low permeability X oil field located in the southeastern part of the Kurdistan Region of Iraq and its field development planning (FDP) challenges. An integrated laboratory study of low permeability carbonate reservoir rocks (dolomitic limestones) included a digital rock (DR) workflow that accelerated the time to complete core analysis program while bringing vital information about the pore-scale flow dynamics. The DR workflow combined high-resolution digital rock imaging, digital fluid models of reservoir brine and live oil samples, detailed wettability model for sample aging and boundary conditions in digital coreflood experiments. DR imaging spanned from micro-CT for meso- and micropores to high-resolution SEM imaging of submicrometer porosity. Direct HydroDynamic flow simulator was used to model multiphase flow in digital experiments by solving equations of the density functional hydrodynamics (DFH). These equations are conservation laws for the mixture of chemical components, momentum, and energy with constitutive relations involving Helmholtz free energy or the entropy functional. Samples were prepared for DR analysis and their representativeness was verified by obtaining routine properties of original plugs, trims, and mini-plugs selected for high-resolution DR imaging. We established the routine core analysis (RCA) properties of samples using DR and compared them with experimental data. Porous plate digital experiments were performed to obtain air-brine capillary pressure curves on all samples, with DR data verification with laboratory data on selected samples. A set of steady-state (SS) relative permeability digital experiments were then performed with live fluids at reservoir conditions. DR models were first fully saturated with brine and then de-saturated to water saturation that matched reservoir water saturation estimated from well logs. The SS cycle was performed after extended aging to establish a mixed-wet condition. SS relative permeability curves were obtained for all studied samples. DR modeling enabled looking at the dynamic changes of phase saturation in pores and significantly accelerated the laboratory program by performing porous plate tests 100-500 times faster and SS tests 20-50 times faster than conventional analysis using live fluids at pressure and temperature conditions surpassing operating ranges of laboratory equipment. The comprehensive combined study (both laboratory tests and DR analysis) results determined the reservoir flow properties within the entire permeability range. It allowed to reduce uncertainties in predicting production levels, improved the forecast quality of the hydrodynamic model and reduced the difference between the minimum and maximum estimates of geological and recoverable reserves.

Авторское право 2015 г., Общество инженеров нефтегазовой промышленности Этот доклад был подготовлен для презентации на Российской нефтегазовой технической конференции SPE, 26 -28 октября, 2015, Москва, Россия.Данный доклад был выбран для проведения презентации Программным комитетом SPE по результатам экспертизы информации, содержащейся в представленном авторами реферате. Экспертиза содержания доклада Обществом инженеров нефтегазовой промышленности не выполнялась, и внесение исправлений и изменений является обязанностью авторов. Материал в том виде, в котором он представлен, не обязательно отражает точку зрения SPE, его должностных лиц или участников. Электронное копирование, распространение или хранение любой части данного доклада без предварительного письменного согласия SPE запрещается. Разрешение на воспроизведение в печатном виде распространяется только на реферат объемом не более 300 слов; при этом копировать иллюстрации не разрешается. Реферат должен содержать явно выраженную ссылку на авторское право SPE.

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Predicting naturally fractured carbonate reservoir behavior is associated with fluid flow modeling of two and more mediums. Presence of highly conductive faults and fractures complicates the process. These complications are generally addressed by common approaches using DPDP models and modern techniques of explicit discrete fracture networks (DFN) modeling. Dual porosity-dual permeability (DPDP) models do not provide proper results without significant modifications and improvements. Flow simulation of the whole fracture set in discrete format on full-scale models is computationally intensive and time-consuming task thus not applicable for practical purposes. Alternative hybrid modeling approach based on combination of individual DFN objects (faults and long fractures) with traditional DPDP modeling was created based on detailed geological static model. Full scope of available geological, geophysical and production data was used to provide background for flow simulations. Numeric algorithms were optimized for three mediums including single porosity medium (SPM), fracture medium (DFN) and discrete objects representing irregular fault and long fracture systems. Generalized workflows for creating static model, defining fractured zones and explicit discrete objects, followed by DPDP-DFN hybrid modeling are described in this paper. The proposed approach was utilized to perform full-scale model history matching, optimize well locations, estimate risks and uncertainties of gas injection efficiency.

This paper concentrates on integrated approach to perform block-factor analysis of oil field development. Particularly a simple and effective method of monitoring of oil field development is proposed. This method permits not only to detect the reasons of production decline and find out problematic wells, but also to forecast the development parameters of oil field, its sections, blocks and cells (elements of waterflooding system).The commonly used method of block-factor analysis is taken as a basis. This approach is strongly worked over, revised and automatized by the development of an integrated program module in VBA programming package. In this paper principles of dividing the oil field into blocks are substantiated, an approach to forecast the liquid production and reservoir pressure is developed, a method of evaluation of the recovery factor, recoverable reserves and oil production forecast using the adjusted displacement water-into-oil curve model is proved. The mathematic base of program module consists of physical processes of oil field development, particularly, models of material balance, filtration equations and PVT-correlations. The realization of this approach come down to sequential performance of following actions: adaptation of material balance model, including the adaptation of PVT-parameters and the definition of timeout value of production response to injection, adaptation of modificated El-Khatib model using real displacement characteristic, forecast and retro-forecast of main parameters of oil field development. The forecast of reservoir pressure permits to calculate the target injection (compensation) level to maintain the required reservoir condition. A block rating approach is developed in order to define the most problematic sections of oil field that require operations to improve the development system effectiveness.A special attention is paid to factor analysis performance. Influence of well stock change, operating factor variation, variation of watercut, liquid rate, reservoir and bottom-hole pressure, well productivity (skin factor) are considered. Factor analysis combining with adjusted displacement curve provides an opportunity to divide oil rate loss by reasons of natural and forward watercut growth.Using of improved approach for oil field development monitoring permits not only to reduce the labor inputs, that are essential for analysis, but to improve the quality of work, to connect the aspects of exploitation of different field areas with geological conditions. It also assists to organize justified and well-timed recommendations to perform workover program, waterflooding system control and to achieve project oil production levels overall.