Injection of water into a rock formation is a common oilfield services technology to maintain high reservoir pressure and increase ultimate recovery of hydrocarbons. While flowing through the well from surface to the rock formation, injected water typically transports fine particles, for example, fine sand grains and calcite precipitated at surface pipeline conditions while mixing water from different sources (e.g., fresh, Cenomanian and formation brine). In the framework of the two-fluid approach to suspension flow modelling, we formulate mathematical model for linear filtration of a particle-laden suspension in the vicinity of a fractured flooding well and transport of ion concentration (salinity). Two major factors of well injectivity decline are described, namely, particle trapping with associated reduction in permeability and porosity of the rock as well as the effect of salinity of injecting water leading to clay swelling, calcite precipitation and change of relative permeabilities of the rock with respect to water and oil. We calibrate suspension filtration model against in-house experiments on clogging of artificial and natural rock cores, in which the profiles of fines concentration along the cores are obtained using X-Ray computed tomography and analysis of 3D rock reconstruction images. The water injection model is adopted to conditions of Priobskoye oilfield of Western Siberia by using the results of standard laboratory experiments on fluid-fluid (calcite precipitation) and fluid-rock (clay swelling, migration of internal fines) compatibility, as well as the effect of salinity on oil displacement and analysis of solid fraction in the injecting water. The calibrated model is then used to describe field data on dynamics of injection rate of three flooding wells. It is obtained that the simulations predict the long-term injectivity dynamics of the wells very well, while at early times (up to 5 months from the start of injection) the model underestimates the injection rate. While fitting the model to field data, we varied only two parameters, namely, solids concentration in the injecting water (in the range provided by lab experiments) and trapping coefficient (the range is limited to result of experiments made with target rock cores). It is demonstrated that only a combination of injectivity decline factors allows to describe the long-term flooding rate of the wells. Ignoring either particle trapping or salinity effects lead to significant overestimation (up to 50%) of the long-term injection rate. Parametric study of water injection showed that two-fold increase in solids concentration in the injecting water as well as oil compressibility lead to similar decrease in long-term injection rate of a well.

Summary Bottom hole pressure prediction is crucial issue in integrated field modeling. This article proposes a new approach to well modeling implementing machine learning algorithms. In this paper bottomhole pressure is analysed as dependent variable on four parameters such as level of wellhead pressure, flow rate, gas factor and water cut. The model is developed using the "Random forest" approach with gradient boosting. The model was tested on synthetic and real data from different wells and fields. The prediction accuracy satisfies company requirements and is more than 90 times faster than traditional empirical correlations.

The article discusses a new technique for optimizing the calculations of the integrated model, all stages of the calculations are analyzed. The analysis of the necessary input data for the integrated model is carried out and the definition of the calculation results according to the obtained method is given. Comparison of calculations using the developed method and a commercial package is obtained. Opportunities for applying the obtained solution are proposed.

Abstract The purpose of this work is to identify the reservoir parameters at which efficiency of the line development system using horizontal wells with multi-stage hydraulic fracturing with waterflooding is lower that efficiency of the depletion drive development. The key factor reducing efficiency of developing such objects using the waterflooding methods is low reservoir pressure conductivity and, therefore, relatively long time of well productivity response to injection. The authors use NPV as a criterion of development efficiency. A certain example (low-permeability reservoirs of the Priobskoye field for which oil production is calculated using the methods of numerical hydrodynamic modelling) is considered. An analytical technical and economic model of low-permeability reservoir development in the depletion and using waterflooding with dimensionless parameters has been also built. For each type of impact on a reservoir, the optimum parameters of the development system shall be determined to further compare efficiency of the depletion and development with waterflooding. The results of calculations based on the numerical model have been summarized in the form of a dimensional chart to determine efficiency of waterflooding low-permeability reservoirs of the Priobskoye field. The results of application of the analytical model are provided in the form of a dimensionless chart.

Summary We continue to intensively study the flow of suspension in the vicinity of injection wells, with the focus on colmatation and particle mobilization in the near-wellbore zone. The key application is the design and planning of operations on improvement of injectivity during water flooding to maintain the reservoir pressure for efficient production. The key phenomenon in focus is formation damage. A 1D three-continua model is used for suspension filtration to describe the permeability damage in the near-wellbore zone. In contrast to the models known from the open literature, the present model is constructed in the multi-continua approach. The carrier phase, the suspended particles, and the trapped particles are considered as three different media. The application of the multi-continua approach allows one to reduce the number of free tuning parameters, which require calibration against experimental data. The model takes into account the effects of trapping of particles in pores (colmatation) and mobilization of particles when the flow velocity exceeds a certain threshold. We continue the calibration and tuning campaign started earlier on a vast amount of various laboratory data on suspension flows in porous medium (core flooding experiments). Simulations are conducted to evaluate the reduced permeability, the concentration of suspended particles and the concentration of trapped particles in pores in the near-wellbore zone. In addition, we calculated the integral skin-factor as a parameter characterizing the colmatation of the near-wellbore zone. A parametric study is carried out to investigate the colmatation of the reservoir in the course of a cycling injection regime where long periods of water injection are interchanging with short periods of production. A free parameter of the model (the colmatation coefficient) which characterizes the intensity of the particle trapping in pores depends on the combination of the properties of the porous medium and the particles (including characteristic size of the pores and the particles). To sum up, we propose the model of multiphase filtration, which takes into account particle trapping in pores (colmatation) and particle mobilization. The tuning parameters of the model are the colmatation coefficient, which characterizes the intensity of particle trapping in pores, and the mobilization coefficient determining the particle mobilization rate. The model went through substantial validation on lab data. The prototype of the simulation kernel allows one to optimize the regime of flooding on injection wells and also to select optimum properties of the particles, fluid, and injection/production rates to avoid dramatic decrease in the injectivity of the injection wells, which occurs due to the permeability damage in the near-wellbore zone.

We consider the filtration of raw water in a formation surrounding injection wells in oilfields of Western Siberia. The mathematical model for suspension filtration developed earlier on the basis of tree-continua approach allows to describe the permeability damage and recovery due to trapping and mobilization of externally-introduced fines. As compared to classical deep-bed filtration models, the proposed model takes into account the filtration of the carrier fluid through the pack of trapped fines and uses only two free parameters to describe the particle trapping and mobilization rates. It has gone through a thorough validation campaign against experimental data with contamination of porous samples by external fines and mobilization of pre-seeded particles in sand packs. Simulations of permeability dynamics in the zone surrounding injection wells are carried out using the values of free parameters obtained by tuning the model against available lab experiments. Both continuous and periodic water flooding/cleanup is modelled. It is found that there are periodic regimes of water injection, in which the permeability of the rock is not damaged. The study will be continued after the calibration of the model against thorough laboratory tests with natural cores and field tests of injection rate dynamics in flooding wells.

Abstract One of the key fundamental problems in using in jection wells to maintain the reservoir pressure for efficient roduction from oil and gas wells is the colmatation of the near-wellbore zone, which results in the permeability damage, and, hence, the decrease in the injectivity. In these cases one needs to increase the pumping pressure or introduce additional filtering systems on surface, which generally increases the cost of field development. For optimization of the flooding process, it is proposed to use a combined approach based on modeling of suspension filtration with account for colmatation of the near-wellbore zone and applying a cycling regime of injection. A 1D three-continua model is proposed for suspension filtration to describe the permeability damage in the near-wellbore zone of injection wells in the fields of Western Siberia. Governing equations are derived using the multi-continua approach. The carrier phase, as well as the particles, which are being transported and deposited, are described as three distinct continua in terms of field variables. The application of the multi-continua approach allows one to reduce the number of free parameters of the model. The model takes into account the effects of sedimentation (trapping) of particles in the pores (colmatation), mobilization of particles at the velocities higher than a certain threshold value. The model has gone through a thorough validation campaign against significant amount of experimental data with contamination of porous samples by suspensions (core flooding experiments) and mobilization of pre-seeded particles in sand packs. Experimental study of self-colmatation of cores produced from Vendian deposits in one of West Siberian oilfields during the injection of a particle-free fluid. It is found that at a fixed filtration rate, the permeability of rock cores decreases and levels off. An increase in filtration rate results in further decrease of the permeability. In order to reproduce the experimental data on self-colmatation, the three-continua model of filtration was modified to take into account two types of deposited particles: particles attached to pore walls, which are the source of migrating particles, and the particles plugging or bridging the pore throats, which reduce the permeability of the porous medium. The numerical simulations showed that the modified model allows to reproduce the self-colmatation of natural cores, the values of free parameters were found by tuning the model against theobtained experimental data. We carried out the simulations of distributions of reduced permeablity, concentration of suspended particles and the concentration of trapped particles in pores in the nearwellbore zone at continuous and periodic water flooding. It is found that there are periodic regimes of water injection, in which the permeability of the rock is not damaged. The study will be continued after the generalization of suspension filtration model to describe colmatation of a rock both by external and internal fines as well as the calibration of the model against data of experiments carried out using on natural cores.