Perm Journal of Petroleum and Mining Engineering

Data of experimental core study for a number of fields of Bashkirian dome is analyzed. Dependencies between parameters of porosity, bulk density and permeability of rocks are established. A representative series of core samples of Visean sandstone are divided into classes of tight formations (non-reservoirs), porous (granular) and super permeable reservoirs by linear discriminant analysis. Application of rock density parameter as an additional criterion to predict permeability values is justified. Each class of reservoirs was statistically analyzed. It is determined that permeability of tight formations (1st class) and super-permeable reservoirs (3rd class) is much less controlled by rock porosity and density than for porous reservoirs (2nd class), that is characterized by stable relationships between permeability coefficients with both porosity and density of rocks. A suggested permeability prediction technique is implemented in construction of a fluid flow model of Visean formation at one of Bashkirian dome deposits where for each reservoir class, multidimensional regression equations were constructed to determine permeability based on integrated effect of porosity and density. A comparison of two calculations of fluid flow models is given. During first calculation permeability is determined by a conventional method. Second calculation is performed by a proposed method where permeability is a function of porosity and density of rocks. Calculations showed a significant improvement in adaptation of a modified model in comparison with conventional approach. Proposed permeability modeling technique is recommended as an initial step in permeability tuning and adaptation of fluid flow model, which consider identified relationships between petrophysical characteristics of a formation.

Regularities on how drilling cuttings block pores and fractures of oil-bearing formation are studied. There are complex physical and chemical processes at well bottomhole occur during entering oil-bearing formation by rotary or rope drilling. That is caused by quality of drilling fluid, intensity of washing, rotation of a drill string, presence of cuttings at bottomhole and a drilling technique. There are hydraulic impulse effects with alternating signs in bottomhole formation zone appear during rope drilling that have a significant impact on quality of work. Underestimation of mentioned factors during entering oil-bearing reservoirs leads to decrease in permeability of oil rocks and well production rate. A clear understanding of physical and chemical processes at bottomhole while entering oil-bearing reservoirs and management of these processes allow to avoid reduce in conductivity of reservoir rocks to a large extent and intensify it in some cases. The main conditions to increase efficiency of oil wells drilling are application of such methods of entering and development of an oil-bearing reservoir that ensure preservation of its natural porosity and permeability or contribute to their increase in bottomhole part of a well. Physical and chemical parameters of oil-bearing formation are the governing factor while choosing its entering and development technology. In recent years, great attention has been paid to issues of entering and development oil reservoirs. Parameters such as geological and physical properties of a reservoir, physical and chemical properties of reservoir oil, rocks and washing liquid, hydrodynamic interaction in an "oil reservoir-well" system are not considered enough in a number of cases during entering and development of a formation. That often leads to incorrect conclusions about a possibility to use actual reserves for needs of national economy. Drilling of oil-bearing formations is a technological process, which create a bore hole in a productive oil-bearing formation for equipment of oil part of a well. Bringing a well on production include technological operations that provide installation of equipment into an oil part of a well and restoration of natural oil permeability of a formation or its artificial increase to achieve maximum production rate of a well.

The paper review efficiency of geological and technological methods (GTM) of bottomhole formation zone (BHFZ) treatment that increase productivity of production wells. Today, according to directional documents, value of skin-effect ( S ) which is determined by calculations based on well-test is the main information to screen a GTM. The greater positive value of S -effect at the same production rates, the earlier it is planned to carry out a GTM on a well. Wells with negative value of S take the last place. The larger value, the less probability of GTM application. There is no relation between S value and parameters of a particular GTM technology. That is caused by physical nature of this dimensionless coefficient. According to directional documents, S gives a generalized virtual assessment of BHFZ state through the principles of good-bad and more-less. Thus, BHFZ characteristics needed to select parameters for a particular technology of GTM application in each well remain unknown. An analysis of real physical objects that constitute structural basis of BHFZ whose properties determine value of S is performed. A historical review of development of this parameter since 1949 is given. It is established that generalized unified characteristic of BHFZ basically reflects its two properties, that are diriment in structural feature that are specific surface of a well drainage system and hydrodynamic resistance of its formation fluid. A technique for determination numerical values of these parameters is proposed. There are examples of application of proposed BHFZ characteristics for analysis of reasons of change in productivity of a production well of Perm region during 4 years of operation and reasons for change in productivity of five more wells after the GTM application are given in conclusion.

Oil of most of domestic and abroad fields is produced by a flooding of oil-bearing formations method. That leads to intensive mixing of oil and formation water and unavoidable formation of persistent water-oil emulsions. Demulsifiers are used to destroy water-oil emulsions and obtain commercial oil in gathering, transportation and treatment systems. In case of high water cut and certain modes of transportation demulsifiers can be a reason of free water formation. Due to its aggressive behavior water can lead to corrosion of a lower part of pipeline system. Therefore, along with demulsifiers a corrosion inhibitor is injected into systems of well fluid transportation. But some demulsifiers, having good washing properties, wash off from internal walls of pipes both an oil film and protective film of corrosion inhibitor adsorbed on them. In turn, some corrosion inhibitors can be emulsifiers, and adding them to a system of intratubular demulsification can have a negative effect on the processes of separation of water from oil. In this regard, compatibility of demulsifiers and corrosion inhibitors is very relevant question. A solution for such problems needs to screen agents that will not reduce demulsifying and protective properties of each other. Oil of South-Khylchuiu field has high paraffin content and positive pour point. So, during transpiration it is needed to take into account that at low temperatures oil reveals non-Newtonian properties. Stop in transportation will possibly show formation of paraffin structures. That can lead to decrease in rate capacity of pipeline and significantly complicate operation. Studies, carried out in the field of transportation of oil with high paraffin content, revealed that in order to improve transportation of high-hardening oil and heavy oil products it is possible to use substances such as flow stimulators (depressant additives). This method does not require large additional capital costs. With a sufficiently wide development of production of additives it can be economically more profitable compared to other methods of transportation.

Increase in complexity and speed of production processes puts forward strong requirements for accuracy of operators' actions, quick decision-making in performance of management functions. Statistical analysis of data on the oil refining industry showed that a refinery with a capacity of 10 million tons of oil per year loses in average $ 4 million only from accidents caused by operator's errors. Around 40 % of accidents and incidents occur due to operator's errors. Reasons for such errors are related to personal qualities, lack of education, training, as well as to factors of low intensity of production environment. A complex of factors of low intensity can lead to hidden up to a certain time “compensated” homeostatic disturbances or modify harmful effect with demonstration of inadequate reactions. The article presents results of study of operators of central control room of two technological departments of high-tech and hazard production (oil and gas) complex to assess combined influence of factors of low intensity of production environment and labor process on work ability and error of actions during labor process. Studies have showed that a long intense functional load on body's systems with influence of factors of low intensity of production environment and labor process lead to development of fatigue and increased tension that operators suffer during day and night shifts. Significant tension of sensory and intellectual systems of the organism with fatigue determines high physiological cost of labor of high-tech production operators. That indicates a need to develop preventive innovative methods to correct a physiological state of operators to improve their performance and take errors off labor, which reduce risk of physical illness.