Russia is one of the main oil producing country in the world with very long history of the oil industry. In one's time in former Soviet Union a lot of attention was paid to oil recovery problems. Unfortunattelly the unfavorable economic climate of the late 1980-s and economic shocks during the period of well-known events in the country in 1990-s caused the rapidly decline of the number of new EOR projects. EOR technologies started to develop in direction of sweep efficiency improvement by cheap agents. Nevetheless by now the very intereresting EOR experience has been accumulated in the country. It is likely that EOR- produced oil in Russia has not already reached its peak level and that it will increase above the current production rates because of improvement of economic situation in the country on the one hand and increasing of mature fields on the other hand. The paper presents an overview of EOR field experiences in former Soviet Union and Russia for the last 25 years, an analysis of recent efforts and discusses briefly on perspectives for conventional and new EOR methods. The main EOR experiences reviewed are chemical flooding (and flow diverting technologies in particular), gas injection, thermal recovery process, microbiological and unconventional EOR. Introduction The problem of enhanced oil recovery is particularly pointed in Russia today: for the last 25–30 years the tendency is from slow to steady decline of the oil recovery factors in the fields. In Fig.1 a dynamics of oil recovery factors over time is presented for the period 1970–2007, derived by averaging the values of oil recovery factors from a significant number of matured fields. The data fields from different regions of Russia had been used for this analysis.
The Pashyian Regional stage (horizon) is the main productive unit of the middle Devonian clastic succession of the South Tatar arch. This article presents, for the first time, maps of the lower and upper parts of the Pashyian, including data on sand-shale ratio, number of sand layers (reservoirs) and thickness, based on the analysis of logging data from 25,000 wells. The maps were created by spatial interpolation of Natural Neighbor and ArcGIS Pro software. The model of sedimentation of the Pashyian Regional stage reflects the interpretation of the plotted maps as well as the synthesis of the results of detailed core investigations (lithological, sedimentological, ichnotextural, petrophysical, etc.) and analysis of archive and published materials. The main points of the proposed model are as follows. The Pashyian sediments were formed in a marine basin, in an environment comparable to that of the middle shelf of modern seas – in an offshore zone dominated by current activity. The basin floor was a relatively flat plateau, on which sandy, silty and clay sediments were simultaneously accumulated. Sediments of all types accumulated during sea transgression. Sea regression caused erosion and destruction of the already formed sediments. Positive landforms of seabed relief, composed predominantly of sandy well-sorted material, comprised autochthonous underwater sand bars, formed by constant currents parallel to the bathymetric contour of the seabed. Underwater sand bars formed extensive systems nearly throughout the entire territory of the modern South Tatar arch. At the same time, allochthonous, poorly sorted, less mature sediments were formed in underwater troughs produced by transversal currents (directed from the shore towards the sea). The proposed model explains the consistent thickness of the Pashyian Regional stage, the mosaic distribution of sand bodies over the area, and the lens-like shape of the sand and siltstone reservoirs. The model can be extrapolated to other stratigraphic intervals of the Devonian clastic succession with similar sedimentological features.
Recently, interest in on-site heat generation has increased due to injection of thermochemical fluids as a complex effect on well productivity. The method of thermochemical treatment with H2O2 while restoring and increasing the filtration characteristics of the bottomhole formation zone is a relatively new and insufficiently studied technology. The article discusses the key factors affecting the exothermic decomposition of this fluid when this fluid is injected into the well. The heat effects, pressure growth and decomposition time of H2O2 were determined depending on the salinity of the water, the composition of terrigenous rock, and various concentrations of H2O2. Physical 1-D modeling of H2O2 injection was carried out on rock models with mobile and stationary oil, which demonstrated a sharp increase in temperature by 100–240 °C caused by the decomposition of H2O2 due to the catalyst and the presence of catalytic active sites in the rock. As a result of this thermochemical treatment, the rock was partially cleaned of immobile oil and heavy sediments. Injection of H2O2 with a catalyst has shown the effectiveness of displacement of mobile oil from the filled sand model. Thus, the results of this study can provide a preliminary assessment of the effectiveness of H2O2 thermochemical treatment in fields operated at a later stage of development.
This article reviews the results of measurement of optical properties of oil, such as polarimetry, refractometric, luminescent-bituminological research, IR-spectrometry and UV-visible-NIR spectrometry used to solve geo-bituminology development of hydrocarbon deposits. The authors pay special attention to optical research in the field of UV-visible-NIR electromagnetic radiation, the results of which allow us to estimate the residual oil reserves, separate production for each formation during the operation of multi-layer objects, determine the producing gas-oil ratio, density and content of hydrocarbons, efficiency of hydraulic fracturing, flow-reducing technologies, and injection of solvents of heavy oil sediments, etc. The published approaches to methods of optical research, which are carried out by laboratories or in-well devices, have been analyzed. This article analyzes the main advantages and disadvantages of current technologies for determining the optical properties of oil. The authors propose wellhead devices for determining the optical properties of oil in UV-visible-NIR radiation (190–1100 nm) and their functional schemes, with a description of the operating principle.
Long-term phased development of a multi-layer field, including tens and hundreds of oil-bearing horizons and local deposits, combined with their vertical and horizontal separation, creates conditions for the formation of residual oil reserves. For the purpose of identifying and spatial localization of residual reserves, an algorithm for retrospective analysis was developed and applied on the example of the Upper and Lower Devonian terrigenous deposits of the Romashkinskoe oil field, which have been developed since 1952. The long history of geological study and development of oil-bearing formations of the Pashiysky D1 (layers g and e), Mullinsky D2, Ardatovsky D3, Vorobyevsky D4 and Biysky D5 horizons is analyzed according to the data of 2605 wells. It is proposed to single out 6 categories of formations and the reserves contained in them. Previously undeveloped formations composed of conditioned reservoirs are classified as category 1. Formations composed of more clayey and less permeable reservoirs are awarded with category 2. Category 3 includes previously developed formations, but left before reaching the limit of water cut, and category 4 – currently being developed intervals. The least promising are those that are stopped after reaching the maximum water cut (category 5), as well as wedged out, replaced by non-reservoirs or considered water-bearing (category 6) formations. Categories were mapped to identify, visualize and describe the main patterns in the distribution of residual reserves, which are established both in single wells and in bypassed oil that include a group of wells. The algorithm was tested on the corporate information base of historical data on geological exploration, research and development of the Abdrakhmanovskaya area of the Romashkinskoe oil field. Examples of experimental workover operations to include the identified residual reserves in the development are given.
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