SU1120178A1 - Method of geochemical exploration for oil and gas deposits - Google Patents

Abstract

A METHOD FOR GEOCHEMICAL SEARCHES FOR OIL AND GAS DEPOSITS, including sampling of rocks, soils or soils, determining the content of chemical elements in them, characterized in that, in order to detect the detection sensitivity and the accuracy of contouring of oil and gas structures, the samples are washed to a gray slurry; the monomineral fraction of pyrite, in which the content of chemical elements, mainly Na, Sc, Co, As, Sb, Hf, Ce, Sm, Lu, Cr, Fe, Au, Eu, and np, is determined, their anomalous distribution is estimated oneness of research 1 x area.

Description

00 1 The invention relates to exploration and can be used to study sections of shallow (50-100 m) wells, pits and zakopushki when conducting a surface geochemical survey. A known method for geochemical prospecting of oil and gas fields includes sampling and disintegration of rock samples and determining the content of alkaline earth metals (mainly calcium) in them, based on the increased content of which, due to the interaction of hydrocarbons with the host medium, anomalies are identified by which the court looks The oil and gas content of the structures under investigation is the disadvantage of the method is that the content of chemical elements in the rock is determined by analyzing the gross sample of the rock. At the same time, it remains unclear what particular mineral is associated with a change in the chemical composition of the sample. The high content of a number of elements present in individual minerals in the total mass of gross samples is significantly underestimated, which reduces the accuracy of the search and, consequently, the effectiveness of assessing the prospects for the oil and gas potential of the territory. The method of geochemical exploration, including the sampling of rocks, is the closest to the proposed method. , soils or soils, determined in: they are spectral emission method of the content of chemical elements, on the anomalous values of which windows are drilled deposits C23. Many minerals of rocks, through which hydrocarbons migrate from the reservoir for a long time, undergo significant changes under the action of a stream of oil and gas molecules. In addition, the occurrence of mineral authigenic neoplasms, distinguishing their chemical composition. The elemental composition of individual minerals, carrying information about the fact of exposure to hydrocarbons, is an important genetic indicator. Establishing certain patterns in the content of individual chemical elements from gross samples of rocks and a large variation of their background is not very effective, and this causes low sensitivity of detection and accuracy of contouring chemical element anomalies over oil and gas fields using a known method. The purpose of the invention is to increase the detection sensitivity and accuracy of contouring of oil and gas fields. The goal is achieved by the method of geochemical prospecting of oil and gas fields, including sampling of rocks, soils or soils, determining the content of chemical elements in them, the samples are washed to a gray concentrate, the monomeral fraction of pyrite is extracted from it, in which the content of chemical elements, mainly Na, Sc, Co, As, Sb, Hf, Ce, Sm, Lu, Cr, Fe, Au, Eu, and their anomalous distribution is estimated by the prospect of petroleum potential of the studied areas. A number of chemical elements have been established, the geochemical properties of which are most dependent on the physicochemical environment determined by the decomposition products of hydrocarbons migrating from oil and gas deposits. Modern analytical methods, in particular, instrumental neutron-cation analysis with the highest sensitivity and accuracy, allow us to study the geochemistry of, for example, chemical elements such as Na, Sc, Cr, Fe, Co, As, Sb, Ce, Sm, Eu, Lu-, Hf, Au, Th, which are geochemical indicators of hydrocarbon migration processes, the anomalous distribution of which by area is a criterion for attributing these areas to promising or unpromising oil and gas. This series of chemical elements is represented by those elements whose behavior is unequal to the deposits of oil and gas and beyond. Anomalous contents of Na, Sc, Co, As, Sb, Ce, Sm, Lu, Hf, Th are characteristic of the deposit’s contour, Cr, Fe, Eu, Au and the absence of Сё, Sm, Lu, Th. In each deposit, it is possible to trace the change in the content of elements, but the more the number of chemical elements from the groups is determined, the more precisely the boundaries of the deposit are established. 3 The method is implemented in the following sequence. Samples of soil, soil or rocks (tpama) with a lithologically comparable composition, volume of 0.02 m (20 - 25 kg) are taken from the buckets, pits or wells during geochemical survey on the search area. The sampled material is crushed and washed to a gray concentrate, from which the monomineral fraction of pyrite is recovered in a known manner. In this fraction, using, for example, highly sensitive and highly accurate instrumental neutron activation analysis, the contents of the chemical elements Ce, Sm, Lu, Na, Sc Co, As, Sb, Hf, Cr, Fe, Au, Eu are determined. The obtained values of the contents are carried on the map and allocate the floor of anomalous, compared with the background, concentrations of chemical elements, a fixed zone of exposure to hydrocarbons migrating from oil and / or gas fields. The Ms of the number of areas with anomalous characteristics of the concentration fields of chemical elements in pyrites includes oil and gas structures. 784 The method was tested within the range of oil and gas in the Kochevne field (Volga region), where the content of chemical elements Na, Sc, Cr, Fe, Co, As, Sb, Ce, Sm was determined in the monomineral pyrite samples with the help of highly sensitive and high-precision instrumental neutron activation analysis , Eu, Lu, Hf, JSC Th. It was found that within the range of petroleum potential the content of such elements as Na, Sc, Co, As, Sb, Hf is 2 - 3 or more times higher than in pyrites behind the contour of the oil and gas bearing deposit, and Се, Sm, Lu, Th characteristic only for pyrites from rocks above the reservoir and not found outside. The contents of Cr, Fe, Eu, Au have the inverse distribution, i.e. in pyrites from rocks behind the contour, deposits 3 and more times (with the exception of Fe content in pyrite) exceed those above deposits. The table shows the distribution of {impurities with impurity elements in monominerapie pyrite samples from Neogene sedimentary rocks of the Kochevne area (Volga region), in g / t.

Sample location

Over the deposit +42.52 +515.0

For contour 13.71 135.0 deposits

Table continuation .

+44.56 +4.42

+0.61

0.25

8.97 Not Detected- Not Found- +0.9 Women

Note. Na, Fe are found in 7 ".

The results obtained confirm the established patterns.

Table continuation

as well as the performance of the proposed method.

Claims (1)

METHOD OF GEOCHEMICAL SEARCHES FOR OIL AND GAS DEPOSITS, including sampling of rocks, soils or soils, determination of the content of chemical elements in them, characterized in that, in order to increase the detection sensitivity and accuracy of the contouring of oil and gas bearing structures, the samples are washed to a gray concentrate, and monomineral is extracted from it. the pyrite fraction, in which the content of chemical elements is determined, mainly Na, Sc, Co, As, Sb, Hf, Ce, Sm, Lu, Cr, Fe, Au, Eu, and their anomalous distribution, the prospectivity g of oil and gas potential is evaluated study areas.