Perm Journal of Petroleum and Mining Engineering

Oil-water contact (OWC) justification is an important criteria for estimation of reserves and evaluation of deposits potential. The main factors that influence evaluation of hydrocarbon accumulation amount are as following: structural surfaces of reservoir top and bottom, effective thicknesses distribution along the thickness of studying reservoir and fluid contact position. In case first two factors are constant accumulation volume and distribution of oil net pay thicknesses in reservoir are controlled by correctly determined OWC. Determination of OWC position is associated with several challenges and mainly with limited initial data. In this paper regional forecast of OWC position was performed. The target of research was Bashkirian dome (its north end in Perm region). Bashkirian dome represents major characterized tectonic element. Accumulated data were generalized on the deposits of presented oil and gas plays (OGP) and resource analysis was performed. During the analysis of OWC position across the all objects of reserve estimation high uncertainty was determined. Statistical sample was the basis for determination of zonal rules and calculation of statistical model of regional OWC. Obtained regression equations take into account formation and tectonic features of Bashkirian dome, allow performing forecast of fluid contact position for more authentic evaluation of hydrocarbon resources of determined structures and specification of WOC in the reservoirs with relatively evaluated OWC that represent 50% from all deposits. Obtained equations help to determine position of OWC that has high uncertainty. Equations will represent additional basis for OWC justification during re-estimation of reserves and evaluation of resources while field exploration. That will increase geological model authenticity and decrease amount of issues during history matching of hydrodynamic model.

Relatively new direction for geological properties study in petroleum geology nowadays is the use of X-ray tomography. The basis of this method is X-ray rock density study. This paper shows the results of possible X-ray tomography applications while studying petrophysical properties of carbonate reservoir plugs on example of several oil fields in Perm region. The microfocus system of X-ray control with computer tomography Nikon Metrology XT H 225 and software AvizoFire 7.0 were used. The cylinder samples with diameters of 30 and 10 mm and cubic samples with a side length of 5 mm were used in the study. The results of X-ray tomography represent 2D-slices of lengthwise and crosswise sample cross-section, 3D-model of cavities, consolidation areas and initial oil saturation distribution as well as graphs of pore and irreducible water saturation versus sample height and histograms of pore diameters. The study of cavities and consolidation areas distribution in the samples allowed to type core depending on its cavity structure. Analysis of porosity evaluation of the samples with different diameters that were made from the one pies of core showed that correlation coefficient was 0.77. Such relatively low coefficient could be explained by significant heterogeneity of core even in one lithotype. During the irreducible water saturation determination four radiographic solutions were tested. It was noticed that irreducible water does not exist in the large voids (cavities, cracks, big pores). Best results were obtained for NaI and LaCl3·3H2O solutions. Presented in this paper results allow obtaining most authentic 3D distribution of pore space and fluid saturation during futhure X-ray tomography study of carbonate deposits.

Current development state of the several fields in Perm region shows low oil recovery coefficient and decrease in possible flooding that could maintain residual oil production at economically reliable level. Water-gas mixtures are used in order to increase development efficiency and oil recovery. Taking into account layered heterogeneous structure of reservoirs and its little thicknesses water-gas mixture could be effectively applied to create significant flow changing barriers. That could increase flooding and, as a result, oil recovery in different geological and technological conditions of siliciclastic and carbonate reservoirs development in Perm region. One of the gas methods of reservoir stimulation is injection of water-gas mixture that contain undispersed or dispersed gas phase. Application of such mixtures increases gas saturation in washed reservoir zones, reduces its phase permeability and rearrange the flow of displacing agents both in thickness and in size. Paper reveals application of water-gas mixture that contain undispersed or dispersed gas phase in order to finish oil displacement from siliciclastic and carbonate plug reservoir models made from two layers. Each of the two-layer models was made from two parallel plug models that model interlayer with low and high permeability. The results of carried study prove the efficiency of water-gas mixtures application for increase of oil recovery from carbonate and siliciclastic reservoirs as well as in flow rearrangement in layered heterogeneous reservoirs. The use of water-gas mixture that contain undispersed or dispersed gas phase leads to increase of displacement coefficient both in low-permeable and high-permeable models. Wherein, use of water-gas mixture with dispersed gas phase leads to higher displacement coefficient and more significant flow rearrangement. Comparison of the results of water-gas mixture application in siliciclastic and carbonate models showed that dispersed water-gas mixture is efficient while injection into both siliciclastic and carbonate reservoirs, application of undispersed water-gas mixture is more efficient in carbonate reservoir.

Nozhovka group of oil fields is located in the south of Perm region. Main factors that complicate development of the fields are as follows: low reservoir permeability and temperatures, high water cut, oil of high viscosity with high concentration of paraffins, sulfur and non hydrocarbon components. The analysis of affected wells that represent 67% of total showed that the main cause is wax deposition that leads to early breakdown of pumps, decrease of well productivity and mean time between failures and cleanings. The paper shows coverage of wells experience wax deposition by technologies that prevent it. Input of inhibitors of wax deposition to the well bottom hole is efficient method to prevent wax deposition. The results of oil and wax samples study from Nozhovka fields group showed oil was heavy and highly-viscous. Wax deposition belongs to asphaltene type. The evaluation of inhibitors efficiency was carried with use of statistic criteria of decision. Based on the analysis results SNPH type of mixtures was efficient inhibitors of wax deposition on the fields of Nozhovka group. The disadvantage of used technology is that there is no universal inhibitor of wax deposition for the oil from Nozhovka group of fields, high specific consumption of inhibitors and continuously changing properties of the producing liquid that require continuous tuning of used inhibitors. In order to decrease the consumption for inhibitor protection from wax deposition it is expedient to select new inhibition compositions with demulsifiying properties and field test of unconventional technologies through injection into well bottom hole and borehole.

In the conditions of Verkhnekamsk and Starobinsk potash deposits the phenomena of gas dynamics that represent sudden stope face rock spelling occur during primary and cleaning mining operations. Sudden spelling of stope face rocks starts from the flat face with rate of less than several tones. Nevertheless, its action threatens miners’ lives and leads to destruction of particular construction elements of valuable excavation and load-haul machinery. At the moment equipping of excavation and load-haul machinery by fence shields cannot protect staff from damaging factors of gas phenomena this kind. The paper shows results of geomechanical justification of application of concave-flat shape of mine stope face for control of sudden face rock spelling during excavation of primary and cleaning shafts. Space modeling of strain-stress state of salt deposits near the stope face of mine excavation was performed on boundary elements method in linear-elastic mode. To solve the problem of strain-stress state of piecewise-homogenous elastic medium by indirect method of boundary elements iteration scheme for border and dual elements was used based on Seidel method. Method included piecewise-linear approximation on triangle elements. During the operating of geomechanical model of linear-deformation medium solution superposition method was used. Wherein, calculation scheme consist of two parts: calculation scheme of virgin rock medium that is loaded by volumetric forces of overburden pressure and calculation scheme for weightless medium with mining with contour that is loaded by volumetric forces of overburden pressure that occur in virgin rock medium and directed towards mining. During the analysis of out-of-limit state of rocks near the stope face integrated criteria of Coulomb was used. Geomechanical evaluation was done for two shapes of faces: concave-flat and flat. It was determined that concave-flat shape of face in comparison with flat one has more stable state of salt rock medium ahead of stope face due to significant decrease of level of stress and deformation massif.