Modern field operation conditions are characterized by a decline in gas production due to the depletion of its reserves, a decrease in reservoir pressure, an increase in water cut, as well as due to the depreciation of the operating well stock. These problems are especially specific at the late stage of development of the Cenomanian deposits of Western Siberia fields, where the anomaly factor below 0.2 prevails, while gas-bearing formations are represented mainly by complex reservoirs with high-permeability areas. When killing such wells, the classical reduction of overbalance by reducing the density of the process fluid does not provide the necessary efficiency, which requires the search for new technical and technological solutions. In order to prevent the destruction of the reservoir and preserve its reservoir properties during repair work in wells with abnormally low reservoir pressure, AO “SevKavNIPIgaz” developed compositions of special process fluids. A quantitative description of the process of blocking the bottomhole formation zone is proposed by means of mathematical modeling of injection of a gel-forming solution into a productive horizon. The well killing technology includes three main stages of work: leveling the injectivity profile of the productive strata using three-phase foam, pumping the blocking composition and its displacement with the creation of a calculated repression. Solutions obtained on the basis of a mathematical model allow optimizing technological parameters to minimize negative consequences in the well killing process.
The paper considers the features of the underground storages (US) construction in depleted oil and gas condensate fields (DOGCFs). The requirements for the structure of the formation, corresponding to the parameters of the object for possible US creation are presented. The influence of geological, hydrogeological, mining and technical rock formation conditions on the reliability and tightness of underground storages, including underground gas storages, has been evaluated. The necessary conditions for the US design are analyzed at the example of the Ach-Su oil and gas condensate field, in the presence of a well-explored trap with acceptable parameters for the construction of an underground storage. An important aspect is the geological conditions that meet the criteria for selecting the object: the required structure, the absence of fracturing faults, high reservoir properties of the formation, a sufficient volume of the deposit for the storage. Geological conditions lay the basis for determining the individual characteristics of the US construction technology at each DOGCF. The refined results for the current gas-saturated pore volume and the rate of pressure drop in the formation are presented, which makes it possible to select improved technological indicators in the course of operation of the created US. In order to select the optimal option for the design and construction of the US, the results of economic and geological scenarios analysis were studied concurrently with the capabilities of the technological operation of the object and transport system, which can ensure the maximum daily production of the storage.
A promising direction for the development of the oil and gas industry is the drilling of small hydrocarbon fields, which constitute two thirds of Russia's total hydrocarbon reserves. When choosing an effective method of development and assessing the potential of small fields in Eastern Ciscaucasia, which are characterized by complex mining and geological conditions with abnormally high reservoir pressures and temperatures, it is necessary to determine the optimal amount of oil production taking into account the flow of edge water under elastic water drive. The article discusses the reasons for the lack of inflows of reservoir fluids in wells during their development, which are due to complex unconventional fractured clay reservoirs in the lower Maykop deposit and the presence of loose rocks in the section of the reservoir. The results of studies of the influence of technological and geological factors on the poroperm properties of the Khadum-Batalpashinsky reservoir are described, zones of rock softening are revealed, the intervals with bottom water and their influence on the well development process are specified. It has been established that the state of the hydrodynamic system of the field depends on the introduction of the bottom and edge waters of the sedimentation basin of the East Stavropol Depression. Oil deposits in the Khadum and Batalpashinskaya suites initially work in an elastic and then in an elastic-water drive mode. The main reasons for the lack of inflows of formation fluids into wells are the low reservoir properties of clay fractured reservoir rocks; clogging of the fracture capacity of reservoir rocks at the drilling in as a result of penetration of drilling mud and its filtrate deep into the reservoir; inflow of formation water from an overlying aquifer with abnormally high formation pressure; the closure of cracks in the clay reservoir due to a sharp decrease in pressure caused by the lowering of the slotted filter into the well; secondary dissection of productive layers by perforation during repression on the formation in a liquid medium with the presence of a solid phase and high density.
Taking into consideration natural depletion of reserves of hydrocarbons in Mesozoic deposits of the majority of operated deposits of North Caucasus and for the purpose of further development of oil and gas producing industry in the region it is necessary to involve a carbonaceous complex of Jura of West Pre-Caucasus with the burial depth of more than 5300 m in the development. When drafting engineering design for a construction of exploratory wells in complex mining and geological conditions driven by anomalously high overburden pressure and temperature, use of thoroughly studied field geological information and taking into consideration the experience of boring similar wells is important. The paper provides analysis of geophysical data, the results of complex studies of reservoir porosity and permeability features of rocks picked out of core-samples of the first exploratory well on Krupskaya zone (porosity, permeability, electrical, acoustic, lithological characteristics), pressure-and-temperature conditions. The information obtained allowed to specify technological parameters of boring and tailing-in and to give recommendations regarding the way of exploratory wells boring and use of borehole equipment. In order to avoid the development of significant hydrodynamic pressure in the borehole which provokes gas showings it is necessary to keep on a certain level of minimal values of mud rheology parameters (dynamic shear stress τ = 70¸135 dPa; plastic viscosity η = 25¸35 mPa·s). For the purpose of real-time keeping of overbalance with anomalously high overburden pressure, control and regulation of calculated head pressure a stripper head should be included into the equipment configuration. Furthermore well head equipment and blowout preventer equipment must be designed for expected gradient of overburden pressure.
One of the most important directions in upgrading well productivity in the process of mining hydrocarbons consists in fighting with salt formation and salt deposition. Solving that problem becomes especially actual when operating deposits that are in their final stage of exploitation in complex mining and geological conditions accompanied by deposition of salts in the well foot area of oil bed and their sedimentation on the sub-surface and surface equipment. It provokes a drop in well productivity and results in off-schedule repair works. Specifics are considered of exploiting minor gas condensate deposits of the Northern Caucasus that are operated under complicated mining and geological conditions of anomalously high bed pressures, high temperatures, strong depressions on the beds and inflow of mineralized water from water saturated seams. Processes are studied of salt deposition from heavy hydrocarbons in the well foot and the bed area surrounding it. Water sample analyses data from different wells have demonstrated that the main salts carrier is the associated water, and the principal sedimenting agents are corrosion products, as confirmed by the results of microscopic studies. The dynamics is presented of salt deposition in the “well foot – wellhead – separator” system retrieved from the results of studies of reaction products in the well foot zone of oil bed. It is demonstrated that the efficiency of struggling with salt deposition in the course of mining hydrocarbons depends on comprehensive approach to the problem, the principal thrust lying with prevention of such deposition. Possible ways are considered to prevent precipitation of ferric compounds in the course of operating gas condensate wells, a way is suggested to intensify gas inflow.
