RU2117318C1 - Method of searching and prospecting fluid minerals - Google Patents

Abstract

FIELD: oil prospecting. SUBSTANCE: when developing oil-and-gas and hot-springs deposits, first, heat conductivity of gas-, oil-, and water-saturated samples of drill core material of local rock is measured. In laboratory conditions, temperatures and pressures of bed are simulated in dependence of combined effect of measured parameters and chemical nature of saturating medium. Then, using value of measured parameter, one determines heat conductivity of compositionally different lithologic complexes under deep bedding conditions and plots found results on local geological map. Distribution of heat conductivity across the map will indicate abnormal plots of fluid deposits. Reliability of useful volume of deposit is revealed by determining natural porosity. EFFECT: improved prospecting accuracy. 2 cl

Description

 The invention relates to geophysics and is intended for the search and exploration of fluid mineral deposits, can be used to increase the efficiency of the development of oil and gas and geothermal deposits.

 There is a method of searching for oil and gas deposits (ed. St. USSR N 1004943, 1983), by identifying deep-root pipe-like channels in the subvertical zones of tectonic crushing, drilling is carried out in areas affected by these channels. This method is not suitable for the search and exploration of deposits in areas not subject to tectonic crushing.

 A known method of geological exploration, using electronic spin resonance signals obtained from hydrocarbon reservoirs (US patent N 4607014, 1984), by exposing the samples from boreholes to the appropriate effect to excite electrons in the samples, while proceeding from the graphs of the trajectories of possible migrations, determine sources of marked samples showing the presence of enhanced ESR signals, the direction and depth of underground oil strata. The disadvantage of this method is that it does not allow the search and exploration of water-gas-bearing deposits and reliably identify the useful volume.

 Closest to the proposed method is the search and exploration of fluid mineral deposits using geothermal parameters that characterize the possibility of its implementation (Sokolov V.L. et al. Searches and exploration of oil and gas fields. -M .: Nedra, 1974, p. 57, 166, 181, 208, 210), by studying the heat flux that generates over the geological structures of the deposits near the surface of the earth, reflecting various structural features of the earth's crust. The intensity of the heat flux near the surface of the earth depends on the energy saturation of the earth's crust in a given area, on the thermal conductivity of the rocks and on the geological structure. Next, the parameters of the deposit are determined for calculating reserves and spatial variability of geological and industrial parameters by objects (horizons, etc.). The disadvantage of this method is the low efficiency and reliability, which consists in the fact that using the parameters shown without signs of funds and methods for their study. He does not consider the possibility of searching for geothermal deposits and does not reliably identify useful volume at depths not achieved by drilling.

 The purpose of the invention is to increase the efficiency of the search and exploration of fluid mineral deposits and the reliability of identifying the useful volume of these deposits.

 This goal is achieved by the fact that: 1. Using the previously known method for determining the coefficient of thermal conductivity of substances (ed. St. USSR N 760774, 1980) for a new purpose - using experimental thermal conductivity data of gas-, oil-water-saturated core samples of geological formations of the region, obtained In this way, under conditions simulating reservoirs, the thermal conductivity is determined for lithological complexes of different composition in the conditions of deep occurrence of the reservoirs and its changes are detected at various depths x by applying them to the geological map of the region (thermal conductivity maps). The distribution of thermal conductivity values on the map will show the presence, position and direction of water, oil and gas complexes. Graphic trajectories on the map will reflect the presence of abnormal areas of thermal conductivity and their depth, the maximum values of which determine the central region, deposits of water, oil and gas structures.

 2. Using also the previously known method for determining rock porosity (auth. St. USSR N 1718045) for a new purpose, using rock porosity data from core material of geological formations of the region obtained by this method in reservoir conditions at depth H when identifying the validity of the useful volume of fluid deposits mineral.

где
Q - количество тепла;
S - эффективная площадь образца;
ΔT₀ - перепад температур на образце при выключенных в основном и охранных нагревателей;
ΔT₁ - перепад температур на образце при включенных в основном и охранных нагревателей.The essence of the proposed method is as follows: at the beginning, using the previously known method for determining the thermal conductivity of substances (ed. St. USSR N 760774, 1980), experimental data on the thermal conductivity of gas-, oil- and water-saturated rock samples are obtained as follows. In the measuring cell, a stationary thermal field is set for each temperature; thermostating with the main switched off and security heaters measure the temperature gradient on the sample and determine its direction. The temperature gradient on the sample can be directed both from the heater to the refrigerator, and vice versa. The temperature difference between the main and guard heaters is also measured, determining the direction of the heat flow. Then determine the direction of the heat flux when the heaters are turned on, maintaining a fixed value of the temperature difference between the main and security heaters. If the direction of the measured values of the temperature drops on the sample in the first and second cases coincide, then the first is subtracted from the second value, and otherwise both values are added. The obtained results of the measured parameters are used to calculate the thermal conductivity coefficient according to the working formula of the method:

Where
Q is the amount of heat;
S is the effective area of the sample;
ΔT ₀ - temperature difference on the sample when the main and security heaters are turned off;
ΔT ₁ - temperature difference on the sample when the main and security heaters are on.

 Then, using the obtained experimental data, the thermal conductivity is determined for lithological complexes of different composition in the conditions of deep occurrence of the layers corresponding to a specific depth in the well and its change at various depths is detected by applying them to the geological map of the region. These conditions accept the averaged distribution of temperatures and pressures with depth in the wells. In the nature of changes in the thermal conductivity of water-, oil- and gas-saturated rocks, there is a tendency to decrease with increasing depth, this decrease is the result of the prevailing influence of temperature. However, the degree of this decrease depends on both saturated fluid and lithological composition.

где
m_о - абсолютная пористость в нормальных условиях, %;
m_н - искомая пористость в пластовых условиях на глубине H,%;
λ_o - абсолютная теплопроводность в нормальных условиях Вт/м • K;
λ_н - теплопроводность горных пород в условиях температуры и давления на глубине H, Вт/м • K.Next, determine the absolute porosity of rocks (eg sandstones) using the method for determining the porosity of rocks (ed. St. USSR N 1718045, 1991) as follows. The porosity of rocks under normal conditions is determined using the laboratory method of Melcher. The thermal stability of rocks is measured in a laboratory installation with steady-state thermal conditions under normal conditions and in conditions simulating reservoir temperatures and pressures at a depth H. Then, the porosity at a depth H is determined from the measured parameters, which were not achieved by drilling by the formula:

Where
m _o - absolute porosity under normal conditions,%;
m _n - the desired porosity in reservoir conditions at a depth of H,%;
λ _o - absolute thermal conductivity under normal conditions W / m • K;
λ _n - thermal conductivity of rocks at temperature and pressure at a depth of H, W / m • K.

 In the literature, methods are known for measuring the porosity of other types of geological formations (carbonate rocks, etc.) under normal conditions.

 The material composition of the layers lying at a depth of H is determined on the basis of the study of lithological-facies maps compiled for the studied region.

Claims (2)

 The method of searching and exploration of fluid mineral deposits, which consists in modeling reservoir conditions that simultaneously take into account the effect on the sample of pressure, temperature and pressure of the fluid saturating it, determining the geothermal characteristics and parameters of the reservoir, the spatial variability of geological parameters for the object, characterized in that to increase the efficiency search and exploration of mineral deposits receive experimental data on the thermal conductivity of gas-, oil- and water-saturated samples in the core material of the region’s geological formations under conditions simulating reservoir, then, using thermal conductivity data, this parameter is determined for lithological complexes with different composition in the conditions of deep occurrence of the reservoirs and its change at various depths is detected by applying them to the geological map of the region, with the distribution the values of thermal conductivity on the map will show the presence, position and direction of water, oil and gas complexes, in the graphic trajectories on the map will show the presence of omalnyh thermal conductivity areas and their depth, the maximum value is determined by the central region of deposits of water-, oil- and gas-bearing structures. 2. The method according to claim 1, characterized in that to determine the reliability of the useful volume of the fluid mineral deposits determine the porosity of the rocks by the formula

where λ _o and λ _H - thermal conductivity under normal conditions and at a depth of H;
m ₀ and m _H - porosity under normal conditions and at a depth of H.