SU754280A1 - Method of determining abnormally high pressure zone in seam - Google Patents

Description

The invention relates to the geologic-geophysical forecasting of oil and gas reservoirs and relates, in particular, to forecasting and identifying areas of abnormally high reservoir pressure (AHPF zones) along the section in the process of drilling deep and ultra-deep wells using nuclear magnetic resonance (NMR).

Under AVPD is understood reservoir pressure exceeding the normal (hydrostatic) by 20% and ^ opea. Wiring wells, especially deep and ultradeep, without timely allocation of AHFP zones, their registration and appropriate correction of drilling technology (mode ₍ drilling, density and composition of drilling mud, etc.) leads to an emergency situation.

There is a method of determining the zone of AHP in cross-sections with respect to the travel time of an acoustic wave in clays.

For this purpose, according to the results of studies of this and neighboring wells, indicator acoustic measurement curves are constructed2

With a depth parameter of dpya clay, they are divided into sections of monotonous change of this parameter, corresponding to intervals with normal reservoir pressure, then they interpolate and extrapolate segments of these curves to adjacent ones, on the basis of which they build a normal graph of the parameter being studied. Then, the anomalous values of this parameter, measured in the AHWP zone, are compared with the values obtained for the same depths, according to the normal graph (the reservoir pressure in the reservoirs adjacent to the clays is considered equal to the fluid pressure in the clay pores) {Ϊ].

However, this method is characterized by low accuracy and reliability, it can only be performed intervalwise (between additions after lifting the tool), significant time and labor costs, delay of the information received and, most importantly, the inability to predict AHFP areas directly during drilling (with reverse 75428

influence of the technology of the latter).

The closest to the proposed method is to determine the zone of abnormally high reservoir pressure, based on the study of the properties of rocks in its ₅ • section of the samples, in particular sludge entering the mouth of the drilled well continuously in the process of its penetration.

This method is based on the study of changes in the porosity of clay rocks in the section, which, in turn, is due to Hx flux density. According to this method, stone materials (cores, sludge, etc.) are taken from the well, porosity of these samples is estimated from data of 15 measurements of their properties from traditional methods (electrometric, acoustic, etc.), clay density is calculated in these samples, build a line of normal compaction (LNU) of clayey 20 rocks, in general, in a fairly long interval along the well section, and mark the beginning of the AHPD zone by the deviation of the calculated (by porosity) clay density values from the LNU (21. 25

The known method has insufficient accuracy (the deviation of the clay density in the AHFP zone from the LNU does not usually exceed 20–30% and depends on the depth of the rocks) and the limited reliability in sections with interleaving of clays, sandstones and siltstones / inefficient with a rapid increase clay-density requires the correlation of well log and geophysical research methods, due to the requirement of the presence in the section of sufficiently thick strata of clay rocks (500-800 m and more), depends on stratigraphic disagreement, lithologically x changes (carbonate, sandiness, etc.) and tectonic disturbances.

The purpose of the invention is to improve the accuracy of determination and effectiveness of forecasting areas of abnormally high pressure in the section in the process of 45 drilling of deep and ultra-deep wells for oil and gas.

The delivered chain is achieved by placing the sampled sample of sludge with drilling fluid in a test tube into a nuclear magnetic resonance repaxometer sensor, replacing this fluid between sludge particles in the measuring zone of the sensor with organofluoric fluid, registering the spin-spin relaxation time

and the times of the spi-lattice relaxation of water in the pore space of particles are typical T (and in the free volume T \ _o ,

About 4

establish the lithological affiliation of the rock sample to the clay according to the value of the difference 1 / T ^ -1 / T _4o ^ 60 s "*> estimate the value of the ratio T | characterizing the material composition ^{Λ of} this clay, and determine whether the section of the well section from which the sample under study is selected, zone abnormally high reservoir pressure on the value of the ratio Td

characteristic of illite-type clay, and the discrepancy is in magnitude Td / T ^ p2.

FIG. 1 shows the dependence of the relaxation ratio> 5 = 1 / T _d -1 / T | ₀ , where TD and T _X0 are the measured values of the relaxation times of water in the free state (in volume) in the rock, from residual water density from terrigenous rock, in FIG. 2 - the distribution of clay minerals and the measurement of the ratio eA = Td / T ^ over the well section in the AHFP zone: in FIG. 3 - the same: outside the AHRM zone.

To measure and record the Td and T ₂ times of proton relaxation of pore water in clays, one can use the pulse method and nuclear magnetic resonance equipment.

Measurement of relaxation times for rock samples is most conveniently accomplished by pulsed NMR: time Td - by means of a sequence of two 90 ° pulses, time T- by a sequence of 90 ° and 180 ^σ -Γθ pulses.

The evaluation of the lithological affiliation of the rock sample under study is proposed to be carried out by means of the established dependence of the relaxation ratio / 5 on the residual water content

terrigenous rocks (Fig. 1), with a value close to 60 s ~ ^l and more, indicates a clay type of rock.

To predict and determine the zone of abnormally high reservoir pressure (AHF), it is proposed to use physico-chemical changes in the nature of the clay material away (in the area of normal reservoir pressures) and around the AHF zone, which are caused by lithological replacement of clay rocks of the montmoriplonite type typical of the area of normal formation pressure on clay of hydromica type in the area of AHPD.

five

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The determination of the nature of clay in the sample under study is supposed to be carried out by NMR using the ratio сА = Тд / Т ^: from the point of view of NMR theory, the value o * ~ 1 »θ is explained by the

several correlation times of the movement of pore water molecules, in particular in clay, i.e., its heterogeneity, and from the petrophysical point of view - the nature (material composition) of rock-forming minerals. According to the obtained results, the value of сА about 2 corresponds to clays of montmorilponite nature, and the value of c <about 11 - to clay of the hydromica nature, the value of 2 15

hydropic nature, value 2 <CA <11 - clay of mixed nature (Fig. 2).

Using the proposed method, it is possible to exclude such distorting factors as the effect of carbonate, sandiness, rate of change in the physical properties of clays in the section, tectonic disturbances and stratigraphic disagreements, which significantly improves the accuracy 25 and reliability of determining the AHFP zone.

A method for predicting and determining the AHF area using the NMR method is as follows.

Place the selected rock sample in the measuring tube, which is installed in the NMR relaxometer sensor, and fill this tube with the sample with fluororganic fluid, which displaces and replaces the existing 35 fluid between the rock particles in the measuring zone of the sensor. The time Td of the spin-lattice relaxation of the liquid (water) in the pore space of the sample and in the volume (Τ ,, θ) is measured, the time of the spin-spin relaxation of the pore fluid is measured and the value = 1 / Td-1 / Td _{0 is} calculated from the measured

values of the spin-lattice relaxation time of the pore fluid (water) in the pore space ⁴⁵ and in the free state (in volume).

Estimate the content of bound (residual water θ of the rock sample under investigation by the calculated value by plotting £ M / s, · by value> / θθ s ~ ^A , corresponding to 100%, determine the lithographic affiliation of the rock using the sample _{and the} follow sample to clays. Calculate the ratio cK = Td / T <^ from measured values of the times of spin-lattice Td And spin-spin Τ η_ relaxation pore

In the sample under study, at the value of Λ - 2, the rock containing water is classified as clay ^! montmoriponito-. type, with a cA ~ 11 - to clay of hydromica (ippit) nature. The correspondence of the section of the well section from which the sample was taken is determined by the zone of abnormally high reservoir pressure by the ratio Td-T ^ 11, characteristic of clays and slit type, and the disparity * by the value Td / T ^ close to 2, and the velocity is estimated approaching the bottom of the well to the zone of abnormally high pressure in terms of the rate of change of the ratio Td / T ^ from 2 to 11 for samples taken from this well in the process of its deepening.

Technical and economic efficiency of the proposed method is expressed in increasing the information content, accuracy and reliability of determining the AHFP zone and approaches to it, in expressiveness and efficiency of the information received, in improving the technology and mode of drilling a well, in accelerating its penetration, which will make savings of at least 15 25% of the cost of the well.

Claims (2)

Claim The method of determining the zone of abnormally high reservoir pressure in the process of drilling a well, based on the study of the properties of rocks. in its section on samples, especially sludge, characterized in that, in order to improve the accuracy and efficiency of forecasting, the selected sludge is placed with drilling fluid in a test tube in the sensor sensor nuclear magnetic resonance, replace the fluid between the sludge particles in the measuring area of the organofluorine sensor liquid, record the time of spin-spin relaxation and the time of spin-lattice relaxation of water in the pore space of particles of the sample Td and in the free volume Tdd establish the lithological belonging amb rock sample to clays znacheo difference of 1 / DT-1 / DT ₀ ^ 60 ^, otseyyut size ratio T / / T> Haglin, and determining matching portion well section from which selected sample, the zone of abnormally high reservoir pressure by the value of the ratio Td "11. characteristic of clay Illy ¹ 754280 8 of the conventional type, and the discrepancy is according to the size of 1. US Patent No. 3235026, rank η / T ^ 2. cl. 181-5. 2, Vowa tap) L / K.5aa £ e sZepb ^ lechleu