Formation damage of near wellbore zone, which occurs during different well operations (drilling, workover), has dramatic influence on well productivity. To improve well performance the removal of damage or creation of new channels, which bypass damage zone, is necessary. For solving this issue, the acid matrix stimulation is widely used in carbonate reservoirs. In order to design and optimize stimulation treatments the simulation modeling is widely used nowadays. One of the critical issues, which influence the stimulation efficiency, is estimation of near wellbore damage zone parameters and taking them into account during stimulation design preparation. Usually this zone is described as the uniform zone with permeability, which is different from reservoir permeability. However, in reality its structure is complex and contains at least two damage subzones with significantly different parameters. Moreover, in case of perforation the created channels can have a positive as well as a negative effect on near well bore zone. The influence of these subzones is also not taken into account in used in practice models for calculation of skin factor due to presence of perforation. These factors influence the efficiency of acidizing stimulation and should be taken into account in modeling process. In this paper, we present details of the approach, which takes into account the complexity of near well bore damage zone and its modification during acid stimulation. For this purpose the combined skin factor is introduced that takes into account the present damage subzones with different permeabilities, perforation channels, wormholes, relative permeabilities and viscosities of pumped fluids and their changes during acidizing process. The combined skin factor approach was implemented into created simulator for matrix acid stimulation, which is used successfully in designing and optimization of stimulation operations on the Company's carbonate fields. The paper, in the example of one of the green oil fields, describes the evolution of well completion and stimulation technologies based on acid matrix stimulation modeling and integration of laboratory and field data. The proposed recommendations allowed to reach the values of skin factor up to −5 and involve into production up to 95% of reservoir thickness.

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.

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The paper describes an approach implemented for horizontal wells permanent monitoring to optimize development of carbonate reservoir based on the Prirazlomnoye oil field case study. Technology and results of production and injection wells hydrodynamic monitoring are shown in detail. The described hydrodynamic monitoring technology allowed confirming geological structure of the deposit, to identify pressure communication between injection and production wells and to improve efficiency of development system.