RU2681050C1 - Method of selection of conditional sample of formation water with the help of cable plasters - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: invention relates to oil and gas industry, to the field of well research – a method for selecting conditioned samples of produced water with modern MIC devices (cable plasters testers) for further study of the physicochemical properties of water and the use of the data obtained in the calculation of hydrocarbon reserves (hydrocarbon raw materials). For the implementation of the proposed method, the required module of the MIC device is selected depending on the geological conditions for sampling, the zone of penetration of drilling mud filtrate (PBS) into the formation is estimated, the required volume is calculated and the time of pumping fluid from the reservoir to obtain a standard sample of produced water, control pumping parameters with an assessment of the degree of contamination of the sample online using modules for in-depth analysis of the fluid of the MIC devices, preserving the sample during transportation to the laboratory. Method is also characterized by the fact that before taking a conditioned sample, it is necessary to clean the wellbore zone from penetration of drilling mud filtrate, after cleaning which to take a clean sample of formation water with PBS content not exceeding 5 % and preserve all the initial properties of water during its transportation to the laboratory.EFFECT: technical result consists in increase the efficiency and optimization of exploration, reduce the time and financial costs of their implementation by eliminating the need to test the aquifer of the reservoir in a cased well column.1 cl, 1 tbl, 5 dwg

Description

The field of technology.

The invention relates to the oil and gas industry, to the field of well research - the selection of representative samples of produced water in wells drilled for oil and gas, using modern OPK devices (cable testers) to further study the physicochemical properties of water and use the data obtained in the calculation hydrocarbon reserves.

The method was developed, to a greater extent, for use in wells in the conditions of the shelf of the Arctic and North Seas, but due to the fact that it allows you to take conditioned samples of produced water, it is recommended for use in wells that are drilled, including on land .

The level of technology.

The composition and properties of produced water contained and underlying hydrocarbon deposits affect both the various methods of geophysical research of wells during their conduct, and the coefficient of hydrocarbon recovery during field development. Therefore, obtaining conditioned samples of clean produced water is as important a task as studying directly the properties of hydrocarbons.

The formation water analysis is used to calculate hydrocarbon reserves, dynamic reservoir modeling, as well as for a feasibility study of development efficiency, including the assessment of capital and operating costs in the process of industrial development of hydrocarbon deposits.

Currently, there are a number of regulatory documents containing requirements for sampling water during prospecting, evaluation and exploration work of hydrocarbon deposits. The most detailed requirements for studying the composition of formation waters and presenting the results are formulated in the “Methodological Recommendations for the Application of Classification of Oil and Combustible Gas Reserves and Resources”, Order No. 564 of the Ministry of Natural Resources and Ecology of the Russian Federation “On approving the requirements for the composition and rules for registration submitted for state examination materials on the calculation of oil and combustible gas reserves ”and“ Methodological recommendations on the calculation of geological oil and gas reserves by the volumetric method ”. Requirements for the volume of research and the presentation of the results are also described in the industry standard of Russia OST 153-39.2-048-2003 “Oil. A typical study of reservoir fluids and separated oils. "

According to current instructions, formation water samples for studying physicochemical properties are taken at the wellhead or by deep samplers during testing of aquifers in the production string after perforation. In this case, it is necessary to induce the influx of water by various methods of intensification, to select fluid in two to three volumes of the borehole space and to obtain close parameters in three consecutively selected water samples. The parameters and properties of produced water, selected in this way, are the most representative.

The disadvantages of this method are the relatively long lead time and their high cost, including the cost of utilization of formation fluids. Especially when exploring offshore wells. So, for example, in the conditions of the shelf of the Arctic and northern seas for a short navigation period, there is not always enough time to test productive formations in multilayer hydrocarbon deposits, not to mention the test of the interval with bottom water. Also, it is not always possible to install additional equipment to intensify the inflow of produced water from the well to SPBU (self-lifting drilling rig) and PPBU (semi-submersible drilling rig).

An alternative to the test method in the production casing can be the use of modern devices on the cable for testing seams (OPK).

If earlier, reservoir fluid sampling devices of the previous generation took samples of formation fluids at a given point without the ability to control the influx and pumping of a significant amount of fluid from the reservoir until the moment of sampling, then most often such samples were not conditional. This generation of instruments additionally allows you to monitor various parameters of the pumped-out formation fluid in the surface control mode, pump significant volumes of the formation fluid, have the ability to conduct additional pumping along the peripheral circuit, cutting off the inflow of new filtrate from the well into the pump-out zone, etc. Which made it possible to find a wider one application, including taking standard samples of reservoir fluids.

Modern OPK devices are represented by a fairly wide range of their types. The simplest option is a pressure probe, a version of it has been developed with the possibility of pumping formation fluid through a screening sampling line (focused probe), which reduces the influence of the borehole space and speeds up the cleaning of the bottomhole zone of the mud filtrate (FBI), a two-pack version of the device and the device, which is a packable element with four elliptical ports for pumping formation fluid in diameter around the wellbore (radial probe).

All probes have depth analysis modules for the selected reservoir fluid with the ability to transmit information to the surface online. The minimum set of sensors for quality control of fluid inflow from the reservoir is;

- sensor for resistivity measurement;

- density measurement sensor;

- pH measurement sensor.

Devices can be equipped with additional sensors, if necessary.

The pump module allows you to adjust the desired depression on the reservoir also online, the pump performance depends on the used piston block, which can be replaced to work in conditions with different reservoir properties of rocks containing reservoir fluids.

For different instruments, optimal mining and geological conditions were determined under which they can be used most effectively. For the selection of conditioned samples of produced water, the most widely used are radial and focused probes.

To preserve the sample in reservoir conditions during transportation, it is not enough that reservoir pressure is maintained in the sampler, as when the sample is lifted from the well to the surface, it cools and accordingly the volume changes at constant pressure, as a result of which gases dissolved in water can be released, which can lead to a change in the properties of the selected water. To eliminate this fact, modern samplers use chambers with pressure compensation, which allow you to save the sample in a single-phase initial state.

Disclosure of the invention.

The technical result, the implementation of which the claimed technical solution is directed, is to increase the efficiency and optimization of exploration work, reduce the financial costs of their implementation, including in the conditions of the shelf of the Arctic and northern seas.

According to the current guidelines, formation water samples for studying the physicochemical properties are taken at the wellhead or by deep samplers during testing of aquifers in the production casing after perforation. The presented method will allow to take conditional samples of produced water in an open hole with devices on the cable of the OPK (formation testers on the cable) and exclude testing in the column of the interval of the formation with bottom water and ultimately reduce the time and financial costs of exploration.

The problem is solved by taking a conditioned sample of produced water using modern OPK instruments on a cable in the open hole of a drilled well. Research data on the physicochemical properties of which can be used in calculating reserves and designing field development, the requirements of existing RDs are not violated.

The specified technical result is achieved by the fact that for sampling formation water, modern cable-based OPK devices and samplers with the minimum requirements for them must be used, the necessary module of the OPK device is selected depending on the geological conditions for sampling, the zone of PBS penetration into the reservoir is estimated, the required volume and time of pumping fluid from the reservoir to obtain a conditioned sample of produced water were calculated, pumping parameters were monitored with an estimate of the degree of contamination of the sample in onli mode ne using modules for in-depth analysis of the fluid of OPK instruments, samples were saved during transportation to the laboratory.

The method is also characterized by the fact that before taking a conditional sample, it is necessary to clean the bottomhole zone from the penetration of the FBI, after cleaning which to take a clean sample of produced water with an FBI content of not more than 5% and preserve all the initial properties of the water when it is transported to the laboratory.

The effectiveness of the use of various models of OPK devices for contact with formations depends on the geological conditions and lithological-petrophysical and filtration-capacitive properties (FES) of rocks. Under certain conditions, it is not recommended to use some modules, due to the inability to achieve the expected result. Also, the pumping efficiency will depend on the choice of the used device module and its piston group, i.e. the required volume, speed and pumping time to obtain a sample of produced water with a degree of FBI pollution of not more than 5%. Pumping time is limited by sticking risks and a possible loss of the OPK device.

After sampling into an in-depth sampler, it is necessary to preserve all the properties of produced water in the reservoir conditions, to prevent precipitation and the release of dissolved gases, which will lead to an irreversible change in the properties of the selected water and the impossibility of its recombination. In this connection, it is necessary to use modern samplers with certain requirements for them.

A brief description of the drawings.

In FIG. 1 shows a palette for estimating the pumping volume for a pressure probe. For effective porosity, 20% (if necessary, recalculate proportionally).

In FIG. Figure 2 shows a palette for evaluating depression when testing with different probes.

In FIG. Figure 3 shows a palette for estimating the maximum flow rate of a pump depending on the value of the differential pressure in the well.

In FIG. Figure 4 shows an example of an assessment of the level of mud filtrate in the inflow.

In FIG. 5 shows an example of a volume estimate for purification prior to a conditioned sample.

The implementation of the invention.

This method has already been tested on drilled exploratory sea wells in the Sea of Okhotsk and the Caspian Sea and showed a fairly high convergence of the results on the studied properties of the selected formation water when testing wells in the string and testing the aquifer of productive formations with modern OPK devices.

To implement the proposed method for the selection of conditioned samples of produced water using OPK instruments, recommendations were developed on the selection of OPK instrument modules for contact with the reservoir, depending on the types of reservoirs, lithological-petrophysical, and filtration-capacitive properties of the host rocks. The recommendations are based on the technical characteristics of existing devices and the experience gained with them.

The OPK devices for implementing the method, in addition to the module for contacting the formation, must include a pump that allows pumping fluid from the formation in relatively significant volumes, taking into account the pressure of the liquid column in the well, and a module for in-depth analysis of the fluid with the ability to transmit data to the surface online. The minimum number of required sensors for a quality control of the cleaning of the fluid coming from the formation is: a resistivity sensor, a density sensor for the pumped fluid and a pH sensor for water.

Sampling chambers are recommended to be used with pressure compensation, which helps to keep the selected water samples in a single-phase state all the way from the moment of sampling to the laboratory where the samples are studied. The pressure compensator avoids the release of dissolved gas and changes in the properties of water during cooling, which occurs when the samplers rise to the surface.

At the planning stage of reservoir water sampling, the optimal OPK device module is selected for contact with the reservoir, depending on the expected type of reservoir of the reservoir and its FES, and a preliminary assessment of the volume and time of pumping of the reservoir fluid to obtain a conditioned reservoir water sample is made, a piston pump unit is selected devices with optimal performance for these geological conditions, it is recommended when planning to select a pump with characteristics that exceed the optimal. The depth of the FBI penetration zone can be estimated from the interpretation of a complex of electrical methods for geophysical well surveys (GIS) with probes of different depths of research.

From the beginning of the testing process, after installing the OPK device in the study interval, the module for in-depth fluid analysis is turned on, which allows obtaining continuous values of the parameters of the pumped-out fluids - resistivity, density, pH. With the emergence of a trend for cleaning by registered parameters, the volume and time of pumping are reassessed based on actual data (Fig. 4). At the same time, the accuracy of estimates of both the current FBI content in the inflow and the pumping time increases as the curves of the reference parameters become flat (resistivity, density, pH) and increases during the pumping process. Testing is carried out until the relative stabilization of these parameters (resistivity, density, pH) and achieve the required level of purification (Fig. 5).

Samples taken in sampling chambers with pressure compensation that satisfy the conditions of transportation are sent to the research laboratory. It is recommended that samples be transported to the laboratory while maintaining the temperature during the entire route using special thermal containers. Sample volumes must first be agreed with the laboratory conducting the study.

The method is as follows:

First of all, the OPK device module is selected for contact with the reservoir, depending on the type and reservoir properties (Table 1).

* - recommendations are general in nature, the applicability of a particular module must be evaluated depending on the geological and technical conditions.

Next, a preliminary assessment of the volume and pumping time is carried out depending on the depth of the zone of penetration of the FBI into the formation, the anisotropy coefficient of the permeability of the host rocks (Fig. 1, Fig. 2), and the differential pressure on the pump module (Fig. 3). At fields already at the exploratory stage, when there are already drilled exploratory and appraisal and exploratory wells, it is possible to plan ahead, before mobilizing the defense industry equipment for the well, which will not significantly reduce the cost of carrying out these works. In this case, there are already studies of core material in the field, data on the anisotropy of the rocks and the depth of the penetration zones, perhaps there is experience in working with OPK devices. If there is no data on penetration depth, then it can be estimated using well logging methods performed on drilled wells. At new facilities where there are no drilled wells, an assessment can be carried out only after drilling the first exploratory and appraisal well and recording well logging methods. In this case, it is possible to mobilize several devices and make the choice of modules already based on the fact of drilling, the anisotropy coefficient can be taken only by analogy with deposits at neighboring fields.

The depth of the FBI penetration zone is estimated from the results of electrometric studies of the GIS complex. In particular, it can be established according to the data of focused multi-probe lateral logging or induction logging. The depth of the penetration zone is one of the output values for the inversion of these resistances in order to obtain reservoir resistivity estimates.

Estimation of the required pumping volume is carried out using the software for hydrodynamic modeling, which allows reproducing the cleaning processes when working with OPK devices. For an approximate assessment of the pumping volume and eliminating the need to perform hydrodynamic modeling, at each DIC operation, special pallets are developed with a dependence of the pumping volume on the permeability anisotropy coefficient and effective formation thickness. For each type of defense industry equipment, such pallets must be created separately. For the optimal choice of the OPK device, it is not enough just to estimate the pumping volume, it is also necessary to determine the pumping speed.

The pumping speed depends not only on the volume that needs to be pumped out of the reservoir to obtain clean produced water, but also on the pump performance and differential pressure on the pump, which also takes into account the repression created by the liquid column in the well. To evaluate the pumping rate, depression must first be determined. In this work, palettes were created for certain types of devices that determine the necessary depression at a unit flow rate and unit fluid mobility, for subsequent conversion into the required geological and technical conditions. Also, for each type of OPK device, or rather its piston module, hydraulic characteristics were obtained (the dependence of the pump flow on the differential pressure). For each type of device, similar palettes should be created, according to the results of hydrodynamic modeling.

Based on the obtained estimates of the volume and speed of pumping, the time it takes to take representative samples with a particular probe and piston block is calculated. Then, the appropriate test parameters (probe and test interval) are selected at which time costs will be minimal. In order to estimate the pumping volume in the case of immiscible fluids, in addition to the parameters listed above, it is also necessary to take into account the possible contrast in the viscosity of the fluids and the influence of phase permeabilities, in this case it is necessary to use hydrodynamic modeling in each individual case. When calculating, it is necessary to take into account the limitations of pumping groups by the limits of the total differential pressure. After calculating the required pumping volume and speed (pump flow depending on the total differential pressure), the pumping time is determined, according to these data, the optimal type of OPK device is selected for taking a conditioned sample of produced water under given geological and technical conditions.

In the second place, the pumping parameters are monitored and the degree of purification is assessed during the defense industry. From the beginning of the testing process, after installing the OPK device in the study interval, the module for in-depth fluid analysis is turned on, which allows obtaining continuous values of the parameters of the pumped-out fluids - resistivity, density, pH. During pumping, the volume and time are reassessed based on actual data. Moreover, the accuracy of the estimates of both the current FBI content in the inflow and the pumping time increases as the curves of the reference parameters change (resistivity, density, pH), while for the quantitative assessment of the relative FBI content in the fluid flow, the limiting values of these parameters are calculated by the approximating curve . Testing is carried out until the relative stabilization of these parameters and the achievement of the required level of purification, after which sampling of produced water is performed. Considering that the described parameters directly depend on the salinity of the pumped water, an assumption is made about a linear relationship between resistivity and salinity. To control the level of pollution, the resistivity is converted to the mineralization of the pumped-out fluid for specific conditions. If the pollution level is still estimated without conversion to mineralization, then it is necessary to convert the resistivity into electrical conductivity, taking into account possible temperature changes during testing, affecting the parameter values regardless of the cleaning process. To evaluate the properties of produced water, an approximating function is constructed that takes into account the change in a certain parameter in time; mineralization, electrical conductivity, or fluid density. The obtained function is compared with actual data, from which the percentage of FBI contamination of the pumped fluid is determined. Calculation is recommended to be done in special software; when the FBI level reaches 5%, a conditioned sample of produced water can be taken.

In the third place, the transportation of the selected samples is carried out using pressure-compensated sampling chambers, which help to keep the selected water samples in a single-phase state along the entire route from the moment of sampling to the laboratory where the samples are studied, and maintaining the temperature regime using special thermal containers.

Claims (1)

A method of sampling a conditioned sample of produced water using OPK devices (reservoir testers on a cable), characterized in that the required pumping volume is estimated either in a hydrodynamic modeling package or using pre-created palettes for each type of device taking into account the dependence of the pumping volume on permeability anisotropy , effective thickness and open porosity of the formation, modeling of the well cleaning process is carried out to assess the required pumping volume, the maximum is calculated possible pumping rate for specific geological and technical conditions, a reservoir interval productivity curve is constructed (taking into account a specific probe) using the appropriate palette for each type of OPK device used, taking into account possible contrast in fluid viscosity and the influence of phase permeabilities, after calculating the required pumping volume and speed (pump flow depending on the total differential pressure), the pumping time is determined, these data select the optimal type of OPK device for rejection and a conditioned sample of produced water under specified geological and technical conditions, during the pumping process, the dynamics of changes in the parameters of the pumped fluid is monitored, and for the quantitative assessment of the relative content of the mud filtrate (FBI) in the fluid stream, the limiting values of these parameters are calculated, for which an approximating function that describes the dynamics of the change in the parameter of electrical conductivity or calculated mineralization, density depending on the volume of pumping and, the limiting (true) parameter of produced water (mineralization, density) is estimated based on the results of measurements of the parameters of the pumped fluid, based on the limiting parameter, the current level of FBI contamination of the pumped formation fluid is estimated and, when the level is 5%, a conditioned sample of the produced water can be taken.

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