RU2464544C1 - Method of preparing samples of formation fluid for molecular biological analysis - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: proposed method comprises dividing formation fluid into water and hydrocarbon phases to produce solid hydrocarbon scale. Said division is executed by settling formation fluid at +4°C for 24-72 hours. Then, water phase centrifugation is carried out at 10000-14000 rpm for 15 minutes to use it for DNA isolation and subsequent molecular biological analysis.

EFFECT: higher accuracy and validity.

1 ex, 2 tbl

Description

The invention relates to biology, namely, for the preparation of low-water reservoir fluid of oil fields for molecular biological analysis by separating the aqueous and hydrocarbon phases.

Molecular biological analysis methods are used to study the spread of microorganisms in various habitats. The use of DNA preparations isolated directly from natural samples allows obtaining more complete information about the structure and dynamics of communities. Using molecular biological methods, a significantly greater variety of microorganisms can be detected compared to culture methods in various ecosystems, including oil reservoirs.

Formation fluids produced from oil-bearing horizons may contain formation water. For adequate molecular biological analysis, it is necessary to separate the formation fluid into phases.

There are methods of diluting oil using various chemical demulsifiers (RF patent No. 2282658, C10G 33/08, 2006.01). The separation of crude oil into the aqueous and hydrocarbon phases is also carried out industrially using special apparatuses, using elevated pressure and temperature (US patent 5821406, G01N 33/26, 10/13/1998). The effective extraction of DNA from samples of the hydrocarbon and aqueous phases obtained by such industrial and chemical methods, and reliable molecular biological analysis are difficult due to partial destruction of the DNA and non-compliance with aseptic conditions.

An analogue is the method of preparing samples for molecular biological analysis (APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Nov. 2009, p.7086-7096, A.Gittel, KBSorensen, TLSkovhus, K.Ingvorsen, A.Schramm), in which the samples are pre-separated industrial hydrocyclones (HP separator V-3440) to separate formation water from oil, and then the sample is filtered through a polycarbonate filter (0.2 mm pore size; Nuclepore, Whatman, Kent, UK), the precipitate is used for further DNA isolation. This sample preparation method is not suitable for low-water samples.

A similar in essence and the achieved result to the claimed invention is a method for extracting DNA from an oil-water emulsion (reservoir fluid) (Applied and environmental microbiology, Feb. 2000, p. 700-711 Vol.66, No.2. VJOrphan, LTTaylor , D. Hafenbradl, EFDelong). In the known method, the separation of the formation fluid into the aqueous and hydrocarbon phases is carried out by heating to 70 ° C for 10 to 20 minutes in a 2-liter Teflon separatory funnel, the aqueous phase is filtered on 0.22 mm Sterivex filters. A disadvantage of the known method is that this method cannot be used to prepare samples from a low-water reservoir fluid, which is a thick oily emulsion.

The objective of the present invention is to develop a method for producing samples of low-water reservoir fluid of oil fields for molecular biological analysis, with the aim of improving the quality of the samples of produced water and crude oil, which ensures high reliability and accuracy of the results of the subsequent molecular biological analysis.

The technical result in the implementation of the claimed method is the implementation of this purpose is to obtain samples of various fractions of low-water reservoir fluid of oil fields for molecular biological analysis. The technical result in the implementation of the claimed method is the ability to quickly and efficiently screen industrially important microorganisms in oil reservoirs and develop specific recommendations for reducing the corrosive activity of microorganisms. and improving the efficiency of exploitation of fields with low hydrocarbon reserves using certain groups of microorganisms.

The problem is solved in that the method of obtaining samples of low-water reservoir fluid of oil fields for molecular biological analysis involves separating the reservoir fluid into aqueous and hydrocarbon phases, followed by obtaining samples in the form of crude oil and sediment, but, unlike the prototype, the separation is carried out by settling formation fluid at a temperature of + 4 ° C for 24-72 hours, followed by centrifugation of the aqueous phase at 10000-14000 rpm for 15 minutes, with a view to further use for isolation I have DNA and subsequent molecular biological analysis.

The proposed method can be used for dense low-water oil in the separation of reservoir fluid into aqueous and hydrocarbon phases, when other methods of sample preparation cannot be applied.

An example embodiment of the invention is given below.

Example 1

For analysis, a low-water reservoir fluid of the Stolbovoye field of the Tomsk Region was taken (water content not more than 20%). Work was carried out to determine the optimal settling time of the formation fluid. From the data presented in table 1, it follows that the optimal settling time of the reservoir fluid is 24-72 hours. If kept for less than 24 hours, then only a partial separation of the water-oil emulsion and liquid oil will occur. It is advisable to carry out sedimentation at a temperature of + 4 ° C. If you defend a sample of formation fluid at a higher temperature, then there is a threat of the development of foreign microorganisms in the sample, which will affect the result of molecular biological analysis (Table 1). The upper phase formed after settling (crude oil) is used directly for DNA extraction and subsequent molecular biological analysis. And the remaining suspension containing water is centrifuged. The results for determining the optimal centrifugation modes are presented in Table 2. The most optimal time and centrifugation speed are 15 minutes at a speed of 10,000-14,000 rpm, which provide the most complete deposition of microbial cells on the solid phase and separation of the liquid supernatant. Our proposed method is used for low-water reservoir fluids, when other methods of sample preparation for molecular biological analysis do not allow efficient separation of fractions of the reservoir fluid.

Table 1 Dependence of the efficiency of phase separation of the formation fluid on the settling time at a temperature of 4 ° C and their initial ratio of 1: 1 Settling time (hours) The ratio of the phases (liquid oil / water phase) Result 6 1: 2 Not enough time for phase separation 12 1: 2 24 1: 1 Optimal result 48 1: 1 72 1: 1

table 2 The dependence of the efficiency of DNA extraction from oil-water emulsions on time and centrifugation speed Centrifugation Speed (r / min) Centrifugation Time (min) Obtaining the preparation of total DNA Result 5000 7.5 - Insufficient time and / or inadequate centrifugation rate to precipitate cells on the solid phase and separate liquid supernatant fifteen - 10,000 7.5 - fifteen + Optimal result 14000 7.5 + fifteen +

Claims (1)

A method of obtaining samples of low-water reservoir fluid of oil fields for molecular biological analysis, including the separation of the reservoir fluid into aqueous and hydrocarbon phases, followed by sediment, characterized in that the separation is carried out by sedimentation of the reservoir fluid at a temperature of 4 ° C for 24-72 hours subsequent centrifugation of the aqueous phase at 10000-14000 rpm for 15 min with the aim of further use for DNA extraction and subsequent molecular biological analysis.