# Method of assessment type of fluid saturating the rock

Use: for direct, in-line type definition liquid aggregate pore space of the rock (water, oil, gas or their mixture). Essence: conduct acoustic well logging (S), measure the velocity of propagation and attenuation of acoustic waves. Affect the rock formations constant electric field. The acoustic well logging takes place simultaneously with the application to the layers of rock a constant electric field. System registration sensor probe AM offer in the field of rock in contact with the electrode negative electrical polarity. Types of reservoir fluids and the position of the borders of their section in the reservoir is determined by the nature and amount of attenuation and change of velocity of propagation of elastic waves, which is determined on the basis of the measurement probe AM. Effect: increase the validity and reliability of the method. 1 Il. The present invention relates to borehole geophysical methods determine the position of the oil reservoirs and methods of control over the development of hydrocarbon fields and can be used for direct, in-line type definition prosaposin is asrabadi fields.A known way of forecasting the possible content of liquid in the porous rock formation located at a known depth, including sampling material impact on sample pressure, comparable to hydrostatic pressure observed at the depth location of the breed, the saturation of the samples varying amounts of mud, water, gas, oil, and mixtures thereof, impacts on samples samples of elastic waves in the acoustic frequency range, determining the resonance loss in the degree of reduction of the amplitudes of the acoustic waves, the acoustic well logging, evaluation resonant losses of acoustic waves passing through different layers of the near-wellbore, and a comparison of resonance loss in the amplitude of the elastic waves in the acoustic frequency range between a [1].The disadvantage of this method is that its implementation requires multiple process operations associated with the extraction of core material and a full range of physical laboratory tests to determine the reference values of the resonance energy loss of elastic waves in the acoustic frequency range. This leads to a significant increase in the value CI type saturating the layer of liquid, includes: carrying out in borehole acoustic logging, the determination of the velocities of propagation of longitudinal and transverse waves, the selection of core material, the determination of the density and compressibility of the solid phase core, the determination of the coefficient of compressibility of the reservoir fluid, the magnitude of which is determined by the type of liquid [2]. The disadvantage of this method is in its low economic efficiency due to the necessity of removing the core and full range of its petrographic study.There is a method of geophysical research passable boreholes rocks through observation seismoelectric effect (SEF) that occur in the rocks under the influence of artificial shock: well lower metal electrode, driven by rotating or shaking bonded with him a low-power source, the application to the electrodes of a DC electric field and check the variable electric potential difference at the level of the oil or gas reservoir [3].The disadvantage of this method is in its low resolution type of the liquid that fills the pore space of the reservoir. This modern oil and gas fields are characterized by the in between water - oil, oil and water and gas - oil and gas. In this regard, the manifestations of the seismoelectric effect in these conditions distorted mutual influences of solid, liquid and gaseous component composing the rock collector, and differ little from the values of militia in the empty rock.Closest to the present invention is a method of determining changes of velocities of propagation of seismic waves in rocks saturated with fluids, which consists in the fact that the analyzed reservoir rocks concurrent with the acoustic logging is exposed to a constant electric current (prototype) [4]. In some cases, oil or gas reservoir rocks are presented in the form of lamellar incision, in which the reservoir of small capacity (not more than two meters) alternate with empty impermeable rock, containing significant amounts of clay. In clays the effect of changes of velocity of propagation of elastic waves when exposed to electrical shock, most significantly. Use directly this phenomenon, which is called electroseismic effect (use in the future), leads to erroneous conclusions about the properties of the reservoir fluid and the fluid type, saturating the layer.The problem is solved in that in the method of estimating the type of fluid that fills the reservoir, which includes conducting acoustic well logging, measurement of attenuation and velocity of propagation of longitudinal and transverse waves, the impact on the rock by a constant electric current, acoustic well logging takes place simultaneously with exposure to rock a constant electric current, and the system of the registration sensors are equipped in the area of the electrode negative electrical polarity, and the types of reservoir fluids is determined by the attenuation and the nature of the change of velocity of propagation of elastic waves.The proposed method is built on the well-known phenomenon of the interaction of physical fields of different nature in the body of multiphase geological formations saturated with fluids [4, 5]. The essence of this effect is that when simultaneous transmission through geological rock weak electric current and mechanical influence on the breed, there are some physico-chemical processes that lead to changes in the elastic constants, which is observed in experiments, as the effects of reducing or increasing scaricato can be seen from [4], closely associated with the type of rock, nature, water saturation, and degree of mineralization. In one case, this effect is positive, i.e. the velocity of propagation of elastic waves in rocks exposed to the electric field is higher and the other lower than without it. The amplitude of the manifestations of this effect in rocks saturated clay, significantly more than in clean Sands or sandstones. The filling of the pores of the rock oils derived from oil, dramatically reduces the amplitude of the effect, or not play it at all. Thus, discovered a new physical phenomenon essentially opens up the possibility for the development of technologies for direct determination of the type of fluid saturating the porous rock collector, and the position of the boundary surfaces between water, oil and gas. Because produced water is always mineralized to salt concentrations of at least 5%, the effect is particularly bright works on the boundaries between mineral brine, oil and gas. Moreover, any substitution of oil and gas mineralized solution immediately appears on the amplitude electroseismic effect and serves as an indicator of this process throughout the lifetime of the well.The proposed method of assessment type of fluid, the us is about the new scheme of the acoustic well logging, the principal feature of which is a substantial reduction in base measurements between receivers of acoustic oscillations. This allows registration of the full wave field in the immediate vicinity of the electrodes, through which breed pass a constant electric current. This scheme allows to reduce the magnitude of the electrical potential on the electrodes, so as neighborhood rocks immediately adjacent to the metal electrode, is under the influence of strong non-uniform electric field, due to the fact that the electric field at the electrode is much higher than the average in the near-well space, which significantly increases the amplitude of the effect, controlling the change of the pore filler in the breed and the position of the contact surface of fluid in it.Diagram of the acoustic well logging simultaneously with the transmission of a constant electric current can significantly simplify technology assessment type of fluid filling the pore space of the reservoir, transferring all necessary operations directly into the well without removing and preliminary study of the core material. Thus, pract in rocks of the collector.The proposed method of assessment type of fluid saturating the reservoir, as illustrated in the drawing, which shows a diagram of the location of the emitter, the registration sensors and electrodes for supplying electric current in the rocks surrounding the borehole. The drawing shows: borehole 1, the acoustic probe 2, a radiator 3, the registration sensor 4, a spring 5, the electrodes 6.The proposed method is as follows. In the hole 1 lower probe 2 acoustic logging method (AM), equipped with a transmitter 3, a receiver of acoustic signals 4 and clamping springs 5. Each spring 5 are two electrodes 6 connected to opposite poles of a source of direct electric current, and the upper - negative and lower positive respectively. With the help of springs 5, the electrodes 6 are pressed against the wall of the borehole 1. The distance between the electrodes 6 vertically chosen equal to the interval between the acoustic receivers 4 probe 2. The base of the probe can be standard, for example of 0.4 m distance from the emitter 3 of the probe 2 to the nearest receiver 4 may be of the order of 1 m At a given depth include the probe 2 and spend acoustic logging by registering the full acoustic wave fields posledovatelnosti, opened by the well 1. Then lower the probe 2 at the same depth and again spend acoustic logging of the selected section, but at the same time serves a constant voltage to the electrodes 6 so that the amount of current between them would be no less than 1A, the spacing of the layers of the reservoir, water-saturated. Write acoustic wave signals sequentially through equal length intervals, for example, several minutes. Then the probe 2 is moved to the next depth with the pre-selected step and produce the same procedure until you fully blocked the investigation interval selected in the borehole 1. At each point in depth inside the interval additionally registers the constant electric current.For each of the studied interval build a graph of the time of arrival (interval velocities on the basis of the measurement), amplitude and attenuation of longitudinal, transverse and lamb-stonley acoustic waves from the quantity of electricity passed through the rock, on the basis of the source of experimental material. The variation of these parameters in each point of the investigated interval Rasim solution the velocity of longitudinal and transverse waves increases with the quantity of electricity passed through the medium between the electrodes 6. The behaviour of the amplitudes is inverted character on the 4 receivers located at the positive electrode and the negative polarity, which leads to the change of the coefficient of attenuation of acoustic waves. At the same time, in the layers of the collector, saturated hydrocarbons, there is no significant change in the dynamic parameters and the speed characteristics of the waves under the action of electric field on these rocks. Further isolated areas of significant divergence times, velocities, amplitudes and attenuation coefficients. In each area determine the nature of changes in parameters in the presence of electric current without it by calculating the derivatives of these functions and their sign (greater than, less than zero or approximately zero) is judged on the type of fluid saturating the porous rock zones. If the sign of the derivative is negative (increase in speed), the type of fluid - mineralized water. If the sign of the derivative is positive or derivative is close to zero, then the type of liquid hydrocarbons. The records are selected and periods of abrupt change of sign Pius surface, separating two dissimilar fluids, namely salt water and oil, salt water and gas, and mixtures thereof. At each transition point function of the derivative of velocity change from plus to minus and Vice versa matches exactly one boundary of dissimilar liquids or liquid and gas.Currently, the proposed method is in the pilot testing stage. In all cases, the saturation of the porous rock oil or its substitutes intervals of oil-saturated rock gave close to zero value of the derivative changes of velocities of propagation of elastic waves in the zone of influence of a constant electric current. The transition of the registration sensor from water-saturated to saturated intervals breed is characterized by a sharp jump in the values of the velocities of propagation of elastic waves on both sides of the boundary surface. The amplitude of the surge is greater than the higher salinity of the solution and the value of DC current passing between the electrodes. This reduction of base observations (the distance between the registration sensor) increases the accuracy of determining the coordinates of the boundary surfaces of liquids in porous rock. The number of points switched and in the vicinity of the well.Thus, the proposed method allows to determine the types of fluids filling the pores and cracks in rocks, and, in addition, allows to quantify the presence of boundaries separating fluid fraction between them. The software method AM treatments Express data logging reduces the time of submission of accurate information about the properties of fluids in the strata of the geological section, which reduces the downtime of production wells. This substantially increases the economic efficiency of geophysical works.Sources of information 1. U.S. patent 4354381, G 01 V 1/40, 1982.2. Auth. St. USSR 890316, G 01 V 1/40, 1981, BI 46.3. Auth. St. USSR 140502, G 01 V 1/40, 1961, BI 16.4. Manstein is walking A. K. , sandpipers C. A., Epov, M. I., Nefedkin Y. A. Change in seismic velocities in the field of a permanent electric current. The geologist. and Geophysics. 1999, T. 40, 3, Novosibirsk, SB RAS, S. 465-473 (prototype).5. Manstein is walking A. K. , sandpipers C. A., Nefedkin Y. A. Controlled variation of seismic wave velocities in water-saturated rocks. //Int. Ammonites. Conf. and exhibition. - M.: EAGO SEG, 1997. D2,5. The abstracts.

Claims

Method of assessment type of fluid saturating rocks, including SN, passing through rocks a constant electric current, characterized in that the acoustic hole logs are simultaneously exposed on rocks a constant electric current, and the system of the registration sensors are equipped in the area of the electrode negative electrical polarity, and the types of reservoir fluids is determined by the nature and amount of changes in attenuation and velocity of propagation of elastic waves by calculating the derivatives of these functions, the sign of which is judged on the type of fluid saturating the rock.

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EFFECT: higher reliability, higher precision.

FIELD: oil and gas industry.

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EFFECT: higher reliability, higher precision.

FIELD: oil and gas industry.

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EFFECT: higher reliability, higher precision, higher efficiency.

FIELD: oil and gas industry.

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EFFECT: higher reliability, higher precision.

FIELD: oil and gas industry.

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EFFECT: higher reliability, higher precision.

FIELD: oil and gas industry.

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EFFECT: higher reliability, higher precision, higher trustworthiness, higher efficiency.

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EFFECT: enhanced precision and reduced cost of prospecting.

4 cl, 2 dwg

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EFFECT: increased accuracy.

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EFFECT: higher efficiency, higher trustworthiness.

2 cl, 6 dwg

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EFFECT: increased efficiency of aerial deposit extend and age prediction.

2 dwg