Development of a Methodological Approach to Identifying Petrophysical Types of Complicated Carbonate Rocks According to Laboratory Core Studies

Petrophysical typification of productive hydrocarbon deposits is one of the main stages of building a petrophysical model of a reservoir. For carbonate reservoirs characterized by a heterogeneous complex structure of the void space, the problem of identifying petrotypes is very relevant. An extensive literature review of existing methods of petrophysical typification showed that the most well-known and widely used of them were based on simple theoretical models of the structure of the void space of rocks, which did not allow a full description of complex carbonate deposits. Moreover, the petrotypes identified on the basis of these methods did not agree with the results of microdescription of thin sections. A new methodological approach to the identification of petrophysical types of complex carbonate rocks was proposed, based on the integration of the results of standard (determination of the absolute gas permeability and open porosity coefficients) and special (nuclear magnetic resonance studies) core studies and data obtained in the lithological description of thin sections. The developed approach took into account the main petrophysical properties of rocks that characterize its reservoir potential, as well as the structural features of the void space and the influence of secondary transformations. The proposed methodological approach was applied to distinguish petrophysical types in the section of the Assel-Sakmara deposits of the Yareyuskoye field: six petrotypes were identified and described in detail, combined into four zones (zone of development of healed fracturing, zone of development of leaching, zone of development of leaching and open fracturing, zone of development open fracturing), for each of them, individual dependences of the absolute gas permeability coefficient on the open porosity coefficient and the Leverett J-function on the water saturation coefficient were constructed. The information obtained would allow a differentiated approach to geological and hydrodynamic modeling of a hydrocarbon reservoir.

Directions of Career Transport Development

Since the beginning of the civilization emergence, people began to use the minerals extraction on the surface of the Earth and the rock mass transportation. One of the main tasks of the mining industry is the transportation of an increasing rock mass amount from the quarry, which has caused the need to increase the power and carrying capacity of mining dump trucks. Today, we can assume that the revolutionary period of increasing the carrying capacity in the creation of heavy-duty dump trucks is over. Further improvement of the designs of frame dump trucks is impractical. To create super-powerful dump trucks capable of efficiently transporting rock mass from deep horizons, fundamentally different designs of machines and power plants are needed. The most important requirement for promising machines is to minimize the negative impact on the environment. In its development, mining vehicles have come a long way: a hand wheelbarrow - a horse cart - a truck - a diesel mining dump truck - a diesel-electric mining dump truck - an electric mining dump truck - an unmanned electric mining dump truck. According to the law of the transition from quantity to quality, it can be assumed that the period of increasing the carrying capacity of mining dump trucks has ended (quantitative changes), and a new period of qualitative changes begins (the development of new types of mining transport, an increase in the specific capacity of a power plant, the use of other energy carriers, etc.). An important area is the use of artificial intelligence: robotic dump trucks, self-diagnostic systems, etc. The main requirement for promising machines is to reduce the cost of transporting rock mass and a minimum negative impact on the environment.

Development of Statistical Models for Predicting Losses based on the Characteristics of Discontinuities

A method for predicting losses over the area of the deposit to minimize the risks of accidents and gas and oil and water showings for the Permian-Carboniferous reservoir of the Usinskoye field was developed. In addition, the analysis of the influence of faults on the number of losses in wells during drilling was carried out. Based on the more than 250 wells drilling analysis, it was revealed that a significant problem during drilling was the loss of drilling fluid. This complication was found in 46% of drilled wells. The intensity of the studied losses was in a wide range: from insignificant losses to strong ones, with a complete loss of mud circulation. The faults identified both from well drilling data and from seismic data were characterized by a different number of wells with and without losses. Using the combination of various statistical methods, individual and complex models for predicting losses in wells depending on the distance from the fault were obtained. Using multilevel probabilistic-statistical modeling, the study of the influence of faults on losses was carried out: initially, based on the data of all wells, regardless of the methods for identifying faults - the first-level model; by the method of identifying faults (drilling / seismic exploration) - second-level models; according to the data of individual faults - the model of the third level. At the fourth level, a complex model was built, which takes into account the calculation results obtained at the previous levels of statistical modeling. The presence of direct and inverse dependences of the absorption probability from the shortest distance to the fault was established. Using linear discriminant analysis, the results of predicting the probability of absorption were checked.

Surveying Tasks Solution Automation in the Framework of Mining and Geological Information System Creation at PJSC "Uralkali"

The results of work on the automation of the solution of engineering problems facing the specialists of mine surveying services of the mines of PJSC "Uralkali" are presented. The developed software modules are fully integrated into the corporate mining and geological information system of PJSC "Uralkali" and are grouped into specialized software systems - automated workstations. These complexes are installed at the workplaces of various mining specialists, from the heads of technical departments to employees of departments at mines. In total, 21 software systems were developed, of which three workstations were created for the specialists of the company's mine surveying service. For the mine surveying departments at the mines, an automated workstation "Local mine surveyor" was developed and put into commercial operation, for the department of capital surveying and geodetic works - an automated workstation "Capital mine surveying", for employees of the department of the chief mine surveyor of PJSC "Uralkali" - an automated workstation "Chief surveyor". The software modules that are part of the automated workstations of the specialists of the mine surveying service allow in an automated mode to solve a wide range of engineering problems, due to the requirements of the current regulatory documents. Among them, one can single out such tasks as: processing the results of instrumental survey of underground and surface objects and, on its basis, replenishment of mining and graphic documentation in digital form (2D and 3D); mining planning and design; preparation, editing and printing of standard technical documentation (payroll, tables, reports and graphics); solving issues of safe mining; analysis of the implementation of planned and design indicators of the mining enterprise, etc.

Research of Bare-Free Drilling Fluids

Mining and geological conditions for the development of new fields are becoming more difficult every year. Accordingly, the requirements for ensuring the environmental and technological safety of the drilling process are becoming more and more important. To ensure such a process, it is necessary to use correctly selected drilling fluids with proper characteristics: rheological parameters sufficient for effective cleaning of the well bottom, density sufficient to create back pressure, fluid loss to ensure a high-quality filter cake. Modern environmental requirements dictate the abandonment of hydrocarbon-based solutions. But when using water-based solutions, there are no suitable solutions, especially with their high density, since the use of barite can lead to a decrease in reservoir productivity. In this regard, the analysis of the problem and the search for options for creating water-based drilling fluids, weighted without the addition of barite, having the properties of maintaining the stability of the wellbore, ensuring safe drilling and opening productive formations without damaging the reservoir characteristics, was carried out. Such a solution was found in changing the base of the drilling fluid - highly mineralized fluids or solutions based on saturated brines. Brines must be created on the basis of inorganic salts that have good solubility, for example, chlorides, bromides. Due to the content of salts, the fluids have an inhibitory effect, and depending on the volume of dissolution, the density of the drilling fluids can be controlled. The scientific works of foreign and domestic scientists analyzed in the article have been published over the past five years, which indicates the relevance of this development. The selected compositions are presented and theoretically investigated, which were also tested in the field conditions.

Study of the Influence of Change in the Sandstone and Aleurolite Collector Properties on the Geological Modeling Quality

The initial data when creating both geological and hydrodynamic reservoir models can lead to errors in the modeling results and the subsequent distortion of the economic assessment and prospects of an oil or gas field. In order to improve the predictive reliability of reservoir hydrodynamic models, a core material study for the Tula object of four fields at the Babkinskaya anticline was carried out. The ratio analysis of porosity (Kp), rock density () and permeability (Kperm) for sandstones and aleurolites was carried out. Using a statistical core sampling based on porosity, density and permeability parameters, a separation by sedimentation processes was carried out for all considered lithological differences. For aleurolite and sandstone, we could talk about the differentiation of characteristics in the process of reservoir properties formation. The values of the parameters Kp, and Kperm, determined from laboratory core studies, were combined into a single statistical sample for the possibility of developing a methodology that would be aimed at describing Kperm using the integrated laboratory studies, namely by adding rock to the analysis. As a result of statistical analysis, it was found that permeability in intervals with low reservoir properties was controlled with the same significance degree by both porosity and rock density for all lithological differences. At the same time, the presence of highly permeable reservoirs for sandstones and their practically absence for aleurolites were noted. For all lithological differences, relationships were established between the permeability coefficient not only with porosity, but also with rock density. The methodology for constructing statistical models for calculating permeability from the values of porosity and rock density was implemented separately for the fields of the eastern and western parts of the Babkinskaya anticline. The described approach to taking into account the influence of rock density on permeability made it possible to determine the differentiated influence of lithotypes on the filtration characteristics of the reservoir. When modeling a reservoir, it is necessary to move from linearity to nonlinearity and take into account that the problem of permeability distribution in the reservoir being solved is somewhat more complicated: in different areas, sometimes the permeability is not controlled by porosity in principle, but somewhere only this parameter prevails. The methodical approach was recommended for 3D modeling. Revealing the relationships between the parameters was most important when developing a methodology for tuning the model in the interwell space. The development of a reliable estimate of permeability for the vast majority of wells will significantly improve the efficiency of hydrodynamic modeling. At the same time, it is necessary to comprehensively take into account the identified relationships between the petrophysical characteristics of production layers. The use of the approach to the analysis of petrophysical characteristics will allow obtaining a more reliable and less subjective hydrodynamic model of the formation.

Method for Forecasting the Efficiency of Matrix Acid Treatment of Carbonate

In the international practice of developing hydrocarbon fields, one of the most common methods of influencing the bottomhole formation zone to stimulate the inflow is acid treatment. Despite the significant accumulated experience, subsoil users increasingly face with a decrease in planned and actual increases in production rates after this type of measures, which is due to both the deterioration of the resource base and the adoption of erroneous decisions during their design. It is necessary to scientifically substantiate the design of acid treatments, taking into account individual well conditions and a preliminary assessment of their effectiveness to reduce technological and economic risks. This study presents a method for predicting the result of acid stimulation on the formation based on multivariate regression analysis and laboratory studies on rock samples. Its approbation was carried out on the example of a carbonate production facility of an oil field in the Perm Krai. The obtained statistical dependencies made it possible to determine with high accuracy the potential success of the planned geological and technical measures, to give recommendations on their adjustment to achieve the target indicators. In the course of laboratory experiments, the optimal technological parameters of the impact were identified: the prospects of multi-volume acid treatments were established with the exclusion of the stage of acid aging for the reaction. The integration of the results of mathematical and physical modeling made it possible to select the required design of acid treatments in relation to the considered geological and physical conditions and assess their expected technological efficiency. The developed technique can be used to rank candidate wells, form and adjust targeted programs for geological and technical measures for short and long term periods, and determine the stimulation technology. The described algorithm can be successfully replicated to other fields.

Analysis of the Acid Compositions Application in High-Temperature Carbonate Reservoirs

The use of hydrochloric acid treatment goes back a century. For the first time the company “Ohio Oil” applied acid for formation stimulation in 1895, and the patent for acidizing limestone was obtained by the company "Standard Oil". However, with a significant increase in production volumes, it turned out that acid solutions caused very strong corrosion of downhole equipment. Therefore, the hydrochloric acid treatment method had not been used for 30 years. The discovery by John Grib of “Dow Chemical” in 1931 – slowing down the effect of hydrochloric acid on the metal with arsenic – made it possible to return to this method, and three years later “Halliburton Oil Well Cementing” began to practice acidizing on an industrial scale. As the analysis of the field material has shown, there are many technologies with the use of modified acids intended for acidizing, which are characterized by a high degree of success. Nevertheless, according to the estimates of different authors, the treatments success varies in the range from 60 to 80%, and for repeated treatments – less than 50 %. The urgency degree of the problems associated with acid treatment of the bottomhole formation zone and the tendencies of its development was investigated. Analysis of patent information according to the International Patent Classification for 17 years (from 1997 to 2013 inclusive) for Russian patents and for 15 years (from 1999 to 2013 inclusive) – for American ones showed stable activity of Russian organizations, while foreign organizations showed in this respect a significant growth of interests and achievements. Foreign experts mainly investigated the modeling of acid treatment [6–11], while Russian specialists were more inclined towards service support of acid treatment. It was revealed that there were no methods for calculating the risks of falling out of heavy oil components during acid treatment, depending on the geological and physical conditions of the target.

Determination of the Minimum Measures in the Well to Prevent the Formation of Asphalt-Resin-Paraffin Deposits

An analysis of the formation of asphaltene resin paraffin deposits is presented, criteria for assigning wells to subgroups of the complications type are considered, and a classification of complications in oil production is proposed. Oil is a complex and varied mixture of various hydrocarbons, both light and heavy, in thermodynamic equilibrium under reservoir conditions. In some fields, oil production is not accompanied by the formation of asphaltene resin paraffin deposits on the downhole pumping equipment, while in others it is complicated by them. Methods of preventing the deposition of asphaltene resin paraffin deposits and methods of dealing with them are considered, the research work done to substantiate the use of chemical reagents to prevent the formation of complications in oilproducing wells is presented, the minimum measures for subgroups of the proposed classification, complicated by asphaltene resin paraffin deposits of the fund, are presented. The methods for determining the effectiveness of the asphaltene resin paraffin deposits inhibitors, developed in the PermNIPIneft branch of LLC LUKOIL-Engineering, were briefly presented, on the basis of which the studies were carried out. The results of studies on the selection of reagents and determination of their effectiveness for the production well stock complicated by asphaltene resin paraffin deposits were considered. It was found that during wells operation where the physicochemical properties changed, the effectiveness of the inhibitor significantly decreased and did not reach the efficiency criterion of 75%. So, in oil production it is necessary to periodically, at least once every three years, check the effectiveness of the selected reagents, as well as analyze changes in such parameters of the processed object as: change in the physicochemical properties of the fluid; geological and technical measures at the well; significant increase, decrease in production; involvement or isolation of interlayers, production facilities; changes in reservoir, bottomhole pressure during operation. Approaches for wells are proposed: where, as a result of research, the criterion of the effectiveness of chemical reagents has not been achieved, it is necessary to select other methods to avoid the complication.

Study of Fluid Flow to a Horizontal Well

Recently, it is necessary to note the presence of negative dynamics in the deterioration of the reserves structure for newly discovered fields, and most of the them are classified as hard-to-recover, confined to deposits with a complex geological structure, low permeability, high oil viscosity, complicated by the presence of faults, active bottom waters and gas caps. Hard-to-recover reserves are drilled with horizontal wells. This is primarily because horizontal wells make it possible to multiply the area of fluid filtration due to the increase in the drainage area, due to the extensive contact of the horizontal well section with the rock, allowing to increase the well flow rate many times over. Summarizing the above, horizontal wells are used to develop fields with the following parameters: fields with a thin oilsaturated rim (up to 15 m), with a gas cap and bottom water; fields of heavy oil, with a viscosity of more than 30 mPa·s; fields with low reservoir permeability (less than 0.002 μm2). Under these conditions, linear Darcy’s law cannot describe fluid filtration. Under the conditions of high-viscosity oil and lowpermeability reservoir existence, a certain initial pressure gradient is determined, due to the rheological properties of the filtering fluid and high values of the surface friction coefficient. Under conditions of a thin oil rim and an increased gas factor, the limiting filtration rates due to the dissolved gas regime are observed, and a nonlinear law describes the fluid inflow. One of the main parameters in the preparation of the technical and economic assessment of the reservoir is the flow rate of each individual horizontal well. Analytical methods for calculating the horizontal well flow rate show a high error. It is proposed to take a fresh look at the problem of determining the predicted flow rate of a horizontal well, using well-known approaches for solving this issue. It is rather difficult to reliably predict the parameters of reservoir operation: the horizontal wells productivity obtained with the help of modern hydrodynamic stimulators turns out to be unreliable, which leads to the formation of an insufficiently rational development system. And the arising complications during operation in field conditions have to be eliminated due to significant volumes of material and labor resources. Thus, the development of methods that contribute to obtaining a reliable calculation of production is an urgent task for the oil industry.