Perm Journal of Petroleum and Mining Engineering

The Verkhnekamskoe field of potassium magnesium salts is located within the Pre-Ural foredeep in the territory of the Solikamsk depression. There are a salt deposit located in the upper part of the cross-section and a lot of oil and gas fields below. It is known that the gas factor plays a major role in the process of gas emission during drilling of exploration wells and the initiation of gas-dynamic phenomena during underground mining. For this, all the data given in archival data and reports on prospecting and evaluation work, on gas emissions recorded during the drilling of prospecting wells in the territory of the Verkhnekamskoe potassium salt deposit were collected. They were generalized and used to build a probabilistic-statistical model for forecasting oil and gas potential. The paper considers 18 characteristics of 374 wells associated with the productive salt formations. The characteristics were compared using the Student t-test and the Pearson criterion χ2. At the first stage, individual one-dimensional probabilistic models for forecasting gas content were built. The obtained individual probabilities were the basis for the discriminant function ( Z м) for predicting gas content in the salt layer. The obtained values of the discriminant function Z м were used to build a regression model for predicting the oil and gas potential of Р н( Z м). According to this dependence, Р н( Z м) probability values were calculated for all the 856 wells under study that were drilled for prospecting and exploration. The average value (± standard deviation) of the probability for the class in the oil and gas potential was 0.510 ± 0.068. For the class outside the oil and gas potential, the average value was 0.490 ± 0.070. The obtained models allow to construct gas forecast schemes and a petroleum potential forecast scheme within the Verkhnekamskoe potassium salt deposit.

The design of a hydrocarbon reservoir engineering requires a detailed evaluation of oil and gas reserves and its production. The first stage of design is the construction of a geological model that allows you to determine the amount of hydrocarbon reserves. The second stage is hydrodynamic simulation. One of the goals of hydrodynamic simulation is the study of filtration processes, which depend on many factors. A correct description of these factors will ensure accurate calculations of the main development indicators. Filtration processes are closely related to the physical and mechanical properties of the reservoir rock. These parameters can be evaluated using various methods. One of these methods is measuring the speed of propagation of elastic waves. The article presents the results of laboratory studies that establish the relationship between some physical and mechanical properties of sandstone and the speed of the primary and secondary waves. Dynamic indicators (Young's modulus and Poisson's ratio) were determined based on ASTM D2845-08. The ultimate tensile strength of rocks under uniaxial compression was determined in accordance with GOST 21153.2-84. The tests were carried out on sandstone samples. The purpose of these studies was to evaluate the dependence of the primary and secondary wave velocity on the uniaxial compression strength, dynamic Young's modulus, and dynamic Poisson's ratio in sandstone reservoirs. As a result of laboratory studies, empirical dependences of the uniaxial compression tensile strength (σс), dynamic elastic modulus ( E ), Poisson's ratio (η) and the propagation velocity of primary ( Vp ) and secondary waves ( Vs ) were obtained, which will allow tracking their changes during the entire period of development of oil and gas fields. The obtained values are estimated over the entire measurement range.

At various stages of the development of oil and gas fields, the formation experiences various stress-strain states. Changes in reservoir pressure during development lead to changes in the physical and mechanical properties of the reservoir. The properties of the host rocks are also influenced by the fluids themselves. The process of extracting formation fluid can cause not only clogging of the filtration channels with leached rock particles and precipitation of paraffins and salts, but also a decrease in the strength and elastic characteristics of the rock. The article provides a brief analysis of the works affecting the causes of changes in the physicomechanical and filtration-reservoir properties of reservoirs during drilling and development of oil fields. The technique of theoretical calculation of changes in porosity and permeability of formations is given. To establish the convergence of theoretical calculation methods with real data, tests were carried out to determine the tensile strength under uniaxial compression and filtration experiments on terrigenous samples of one of the fields in Western Siberia. In an experiment to determine the physicomechanical properties, water and kerosene in various proportions were used as saturation liquids. Based on the data obtained, the dependences of the elastic modulus and tensile strength under uniaxial compression on various types of saturation were derived, graphs and calculation formulas are presented. In the filtration experiment with volume compression, the effect of the effective pressure on the permeability of the samples was determined. The dependences of the decrease in permeability on the axial load on the sample are established. The obtained dependencies can be used in the preparation of geological and technical measures for stimulation of inflow and in the management of field development throughout the entire life cycle.

The paper presents the experience in design of engineering of the field complicated by a high level of uncertainty in the geological structure, anomalous properties and composition of formation water and presence of halite in the pore space of the reservoir as well. Maintaining reservoir pressure is one of the prerequisites for ensuring the planned production levels, however, it is not always a trivial task to implement that. The problem of modeling the salinized reservoir in the field of Eastern Siberia with high heterogeneity of the reservoir, low permeability and salinization is considered. The experience of determining the optimal production pattern using modern methods of modeling, analysis and calculation is considered. Multivariate calculations are performed using the hydrodynamic model based on a probabilistic geological model. The technique of choosing the main options for the geological model corresponding to probability 10 was used; 50 and 90 %, taking into account two factors: initial geological reserves and reservoir connectivity. A qualitative and quantitative assessment of changes in the productivity of wells due to complications caused by the loss of organic and inorganic sediments in the bottomhole formation zone (PHFZ). Formation water and mineralogical composition of the rock are analyzed. The analysis data were used to model the formation of organic and inorganic deposits in the bottomhole formation zone due to changes in thermobaric conditions during production and injection of fluid into the formation. Modeling of the formation of a solid phase during fluid filtration in the BHFZ allowed to identify threshold values of the well’s operational characteristics and bottomhole pressure levels, as well as the dependence of the deterioration of the reservoir properties of the BHFZ on the amount of pumped fluid at the selected well operation mode.