Orenburg Oblast, Russia. North Eastern slope of Zhiguli-Orenburg Arch. Lower Carboniferous deposits.
Exploration task; depth of investigation: 1950-2000 m
LFS investigations covered a previously identified field confined to two structures. At the start of works, some prior information was available on three wells (Nos. 314, 315 and 317) within the structures with the presence of oil in the lower Carboniferous sediments, and on a further three wells (Nos. 310, 316 and 322) outside the structures with no oil bearing in the section.
Based on the results of the work, the central part of the eastern structure was characterized as not promising, whilst the western structure was almost completely covered by the oil-promising area according to the LFS data.
The positions of wells Nos. 1-5, 8, 14, 16 and the results of the testing were obtained after the work was completed.
By testing wells Nos. 1-5, 8, 16, commercial oil inflows from the lower Carboniferous sediments were obtained, although well No. 14 fell through the marks and the deposits of the lower Carboniferous were aquiferous.
The subsequent LFS investigation of well No. 14 showed a decrease in the marks towards the central part of the eastern structure and its disintegration into two domes.
The correlation maps presented in the lower part of the slide show the spectra from the reference dry and oil wells and spectra of the study area. Red indicates a high correlation coefficient between the spectra.
Sakhalin, Russia. Sakhalin - Okhotsk Shelf.
Exploration task; depth of investigation: 1600-2900 m
The LFS method can be used in coastal waters and offshore subject to the acquisition of low-frequency microseismic background field data with the use of specialised ocean-bottom seismometers (OBS). The microseismic survey was carried out using a wide-profile deployment formed of three parallel lines of OBSs. The profile traversed from well No. 1, with the presence of oil content in sediments of the Daghi formation, through the Okhotsk Sea to well No. 2, with no oil-bearing features in the section.
It should be noted from the geological features of the work area that during the course of the LFS survey, located along wells Nos. 1 - 2, there was a significant decrease in the markings of the surface of the Daghi deposits, to the order of 1000 m. Therefore, the use of the standard interpretation approach for comparison of area spectra with the support spectra was impossible.
Interpretation of collected data was carried out on the basis of the multivariate 3D modeling technique, which differs from the standard approach in that the most probable model of the oil deposit distribution is determined instead of predicting the oil prospectivity of each layer.
As a result, a map was constructed for a prognostic assessment of the prospects for the oil content of the deposits of the productive layer of the Daghi formation within the LFS survey profile area, on which a single perspective oilfield region was identified. From the west, this area is probably limited to a tectonic disturbance with an amplitude of about 60 m, and from the east - an absolute elevation -2075 m of the structural surface of the reservoir.
The drilling of the well within the allocated oil-prospecting area by the сustomer is scheduled for 2019.
Samar Oblast, Russia. Buzuluk Depression, Lower Carboniferous and terrigenous Devonian deposits.
Exploration task; depth of investigation: 800-3100 m
Based on the results of the LFS study in the area of the previously identified oil field, a single oil-prospecting region has been identified along the Lower Carboniferous-Devonian deposits, covering two uplifts. In the subsequent investigation, the presence of a single region was associated with the distribution of the deposits of the terrigenous Devonian deposit in the direction of the south-eastern uplift. Drilling of wells Nos. 31, 32, 33, 35 within the south-eastern uplift and in the intersecting between the south-eastern and north-western uplifts revealed the commercial oil-bearing capacity of strata DI and DII, with total effective oil-saturated capacities ranging from 7.1 m (well No. 35) to 17.8 m (well No. 31).
Originally well No. 33 was drilled southeast of well No. 31 (on the maps this position was marked as well No. 33_1). However, according to the drilling results, it revealed only a slight oil saturation in the terrigenous Devonian - the DI layer (according to the GIS - data, a 0.7 m sandy clayey layer with low oil saturation). In addition to the oil content of the terrigenous deposits of the Devonian in the well Nos. 31, 32, 33, 35, oil deposits in the Lower Carboniferous sediments were also revealed (layers B0 and B2).
Astrakhan Oblast, Russia. The Caspian Depression. 3D localisation of heterogeneous zones in a vertical section for drilling accidents prevention.
Technological task; depth of investigation: 0-4000m
The LFS method can also be used in technological problem solving. This particular challenge was to identify heterogeneous zones in a vertical section located above an identified condensate pool in order to minimise complications during the drilling of productive wells and avoid accidents.
Due to the presence of developed salt-dome tectonics, the LFS studies were carried out using 3D-numerical modelling, which allowed the prediction of the presence of inhomogeneities above the main productive horizon. Heterogeneity was understood to be the presence of zones of decompaction, layers with abnormally high reservoir pressure and natural or technogenic hydrocarbon deposits.
The obtained results were analysed jointly with the customer, involving data on complications in the drilling process in the wells already drilled. The analysis showed good coincidence of the heterogeneities identified by the LFS method with the intervals of complications in the wells.
Republic of Tatarstan, Russia. Eastern side of the Melekess Basin. Carbonate deposits of medium carbon.
Exploration task; depth of investigation: 900-1000 m
Two structures, located within 6 km of each other, were investigated in an area with identified deposits in the Bashkir-Vereskian sediments on adjacent structures. The western structure is characterized as unpromising from the point of view of hydrocarbon deposits, and within the eastern structure oil-promising areas have been identified that divide the structure into two parts.
The establishment of exploratory drilling after the LFS studies in the south-western domes of the western structure did not reveal oil-saturated objects (during testing, the inflow was not received). However, as a result of drilling the exploratory well within the eastern structure, a commercial inflow of oil was achieved from the Middle Carboniferous Bashkir-Vereskian sediments.
Western Siberia, Russia. Nadym-Tazovsk syneclise. Terrigenous deposits – layer Ю1-1
Exploration task; depth of investigation: 3100-3300 m
A feature of this area of work is a significant number of disconnected deposits, the structure of which is complicated by a large number of discontinuous faults. The purpose of the study was to estimate the halo of the distribution of the oil deposit within the area of drilled exploratory well No. 1.
According to the results of the conducted investigations, nine wells were drilled within the scope of the site. When testing wells Nos. 2-9, commercial oil inflows ranging between 100 and 190 tons/day were obtained. Well No. 10 fell into the zone of tectonic disturbance and the inflow from this well was not received.
Republic of India. Cambay oil and gas basin.
Exploration task; depth of investigation: 2800-3100 m
The LFS studies were carried out at two sites in the western part of the Republic of India. The oil-bearing region of the area is associated with sandy bodies of bar type. Despite the considerable depth and relatively small search facilities, the LFS studies showed their effectiveness. Within the work areas, four wells have been drilled that have confirmed the LFS forecasts.