RU1774989C - Method of estimating oil saturation pressure with gas - Google Patents

Abstract

Usage: in the oil industry, in particular in the field of studying the physical properties of formation fluids in the development of oil fields. SUMMARY OF THE INVENTION: the pressure of saturation of oil with gas is determined by performing on-site investigations of fountain wells on fittings from smaller to larger, while bottom-hole pressure, buffer pressure and annular pressure are measured. According to the increase in annular pressure, when the bottomhole pressure drops, the saturation pressure of oil with gas is recorded. With the pumping method of operation, a change in the operating modes of the well is possible by changing the number of swings or the stroke length of the plunger. Everything else is similar.

Description

The invention relates to the refining industry, in particular to the field of studying the physical properties of formation fluids, and can be used in the development of oil fields.

A known method for determining the pressure of saturation of oil with gas using direct measurements with depth instruments. The boundary values of pressure and temperature that do not interfere with the normal operation of these devices are respectively 300 atm "75 ° C, which excludes the possibility of using them in productive formations lying at depths of more than 3000 m.

Known volumetric (laboratory) method for determining the saturation pressure

formation oil by gas by lowering the sampler from the wellhead with subsequent delivery of samples to the place of analysis at special high-pressure installations (balance vessels), by examining the dependence of formation oil pressure on its volume change at reservoir temperature (V. Mamuna and others. Experimental study of reservoir oils. Moscow: GosINTI, 1960, p. 143). The disadvantage of this method is the complexity associated with the mandatory sampling and subsequent analysis on special equipment.

A known ultrasonic method for determining the pressure of saturation of reservoir oil with gas, involving the descent of a special deep tool to the bottom

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wells for measuring the acoustic properties of the medium (Chernobay L.A. et al. Remote ultrasonic device for determining the saturation pressure directly in the well. Oil Industry, 1980, No. 9, pp. 46-48). The disadvantage of this method is the low accuracy due to the stimulating effect of ultrasound on the bubble formation process, which overestimates the saturation pressure. In addition, the disadvantage can be attributed to the complexity.

A known method for determining the pressure of oil saturation with gas in the reservoir, providing for multiple measurements of bottomhole pressures at various oil rates by constructing an indicator curve (inflow curve) in the coordinates: bottomhole pressure (Rzab), oil flow rate (Ohm), at which the oil saturation pressure o the formation is determined by the transition point of a linear section into a non-linear one (V. Usenko, Oil field research at pressures below saturation pressure. M; Nedra, 1967, p. 44, ed. St. USSR No. 1059154, class. E 21 B 47/00, 1982). The disadvantages of the known method are the difficulty in determining the transition point of the linear portion of the observed curve to non-linear, which reduces the accuracy of determining the pressure of oil saturation with gas in the reservoir, in addition, the enormous complexity of the work, and hence the high cost, therefore, this method is practically not implemented in the field.

Closest to the invention is a method for determining the pressure of oil saturation with gas in a formation (ed. St. USSR No. 625027, class E 21 B 47/00, 47/06, 1976), which includes determining the change in productivity coefficient or depression and recording the value of depression corresponding to the transition from a single-phase to a two-phase filtration mode and saturation pressures are determined from the difference in the formation pressure and the found depression value.

The main disadvantage of this method is the high complexity and, consequently, the cost. In addition, due to special cases when several wells operate in one loop, this method can not be applied. To use this method, highly qualified specialists, i.e. a special team is required. Based on the foregoing reasons, this method is rarely used in production.

The aim of the invention is the high accuracy of determining the saturation pressure

oil and gas, reduced labor costs and costs, the optional involvement of highly qualified specialists, the possibility of operational work.

The goal is achieved in that measurements are made in new fountain wells in various modes, with the diameter of the nozzles changing, starting with a small, sequentially moving to large. Downhole, buffer and annular pressures are recorded on each fitting (flow rate is not necessary, but in some wells it is possible to determine the optimal operating mode), and the saturation pressure is defined as the bottomhole pressure at which the annular pressure increases at transition to a larger diameter fitting.

0 The novelty of the claimed method lies in the fact that in comparison with the prototype it is characterized by a combination of new ones. essential features, in particular obligatory measurement of annular pressure

5 along with buffer; optional metering of flow rates in different modes; determining the value of the pressure of oil saturation with gas as a rare value of the pressure at the bottom, at which an increase in annulus

0 wellhead pressure.

Due to the presence of new essential features, the claimed method acquires new properties that are not manifested by these features in known

5 technical solutions, namely, significantly lower labor intensity compared to the known ones while maintaining the required measurement accuracy; high efficiency of research;

0 the possibility of increasing the measurement accuracy with an increase in the number of measurements on the fittings within a certain range; mass application, allowing to exclude random errors,

5

The method for determining the saturation pressure according to the proposed technical solution includes the following operations: installation of pressure gauges at the wellhead

0 high pressure buffer and annulus; installation of a small diameter fitting on the flow line (depending on the expected saturation pressure ne of a given area); well completion until

5 entrance to stable mode; pressure measurement at the bottom, buffer and annulus, which are recorded in a special log (in the presence of memory meters, it measures the flow rate and is recorded); installation of a new fitting with a larger diameter on the flip

a loop; repetition of all operations; change of fittings with registration of all parameters, which occurs until an increase in pressure is recorded in the annulus:

the saturation pressure will be equal to the bottomhole pressure of the mode at which the annular pressure jump occurred, or it will be between this and the previous modes. His can

but to refine depending on the required accuracy by selecting fittings of the appropriate diameter.

PRI me R. In well No. 3544 of the Kalamkas field, a study was conducted to determine the saturation pressure in the period from 28.IX.90 to 24.XI.90. The following data were obtained:

Rpl - 8.4 MPa ata 5-12.X pcs. 4 mm 16.X6 mm

22.X8 mm

3.XI10 mm

12.XI18mm

14X120 mm

Rzab - 8 MPa RB / Rzat

7.6 MPa

7.4 MPa 122 MPa 6.75 MPa 5.75 MPa

In this case, the saturation pressure corresponds to a bottomhole pressure between 6.75 and 5.75 MPa and a nozzle diameter between 18 and 20 mm. It is possible to clarify the saturation pressure by varying the diameter of the nozzle within 17–20 mm. In a specific case, such accuracy was not required; the optimum mode was determined on an 18 mm nozzle with an Rzab of 6.75 MPa and a flow rate of 56 tons / day.

The economic efficiency of the method consists of the following components:

accuracy of determining saturation pressure - allows you to set the optimal operating mode, and this, in turn, increases the current oil production and final oil recovery;

Reduced labor intensity - on the need for laboratory research involving highly qualified specialists. A single 3-4-ro bit operator is sufficient to determine RNAC.

Efficiency is expressed in the possibility of applying simultaneously to many

, 8 / 5.8 MPa Onefta 0.5 / 5.6 MPa 0.8 / 5.2 MPa 0.5 / 5.0 MPa 0.35 / 4.8 MPa 0.5 / 5.0 MPa

11 m3 / day 16m3 / day 21 m3 / day 22.8 m3 / day 56 me / day 59 m3 / day

wells, which allows faster commissioning of wells in an optimal mode, which leads to additional oil production. In addition, during operation, the parameters characterizing the formation change, and the proposed method allows you to quickly make adjustments.

Claims (1)

The claims A method for determining the pressure of oil saturation by gas by measuring the pressure on the buffer and the bottom with a successively increasing nozzle diameter, characterized in that, in order to reduce the complexity and increase the accuracy and speed of determination, the annular pressure at the wellhead is measured at the same time as the pressure of oil saturation with gas defined as equal to the pressure downhole, at which an increase in annular pressure at the wellhead is detected.