RU2514044C1 - Method of high-viscosity oil pool development - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: in compliance with proposed method, at least two pairs of horizontal injection and production wells with their horizontal sections located in parallel one above the other. Heat carrier is injected via upper horizontal injection wells and, simultaneously, high-viscosity oil is extracted through lower horizontal production wells. High-viscosity oil is sampled one to two times a month at every pair of horizontal wells space apart by 100 to 150 meters. Oil samples are dewatered to analyse oil viscosity. Then, pairs of horizontal wells are selected with oil viscosity differing by 10% and more to analyse the influence of variation in high-viscosity oil of said pairs of well on steam chambers heating uniformity and to control heat carrier injection conditions and product extraction. Yield and viscosity are monitored.

EFFECT: higher efficiency of development.

5 dwg

Description

The proposal relates to the oil industry, and in particular to methods for developing highly viscous oil deposits by producing horizontal wells by heat exposure of a formation through horizontal injection wells, including double-well horizontal wells.

A known method of developing a heterogeneous oil reservoir, including alternating the period of injection into the reservoir of water through the injection well with the simultaneous selection of reservoir fluids through the production wells with a period of selection of reservoir fluids through the production wells upon termination of the injection of water through the injection well (patent RU No. 2095549, IPC ЕВВ 43 / 20, published on November 10, 1997). From time to time, once every 2-3 days, the mineralization of the produced water is analyzed, and water is injected with the simultaneous selection of formation fluids until a stable mineralization of the produced water is achieved. The selection of formation fluids upon termination of water injection is carried out until a stable mineralization of produced water is achieved, equal to the salinity of produced water. This method allows you to more accurately determine the duration of the cycles of water injection and selection of reservoir fluids.

The disadvantage of this method is the low efficiency in the development of deposits of high viscosity oils by the method of steam and heat exposure through horizontal wells.

A known method for the continuous production of viscous hydrocarbons in gravitational mode with the injection of heated liquids (US patent No. 4344485, IPC ЕВВ 43/24, publ. 08/17/1982). The method uses pairs of horizontal production and injection wells parallel to each other in a vertical plane equipped with a string of tubing, pumping coolant, heating the reservoir with the creation of a steam chamber, selecting products and monitoring the technological parameters of the reservoir and well.

The process is aimed at mobilizing and extracting normally immovable, highly viscous oil from tar sandstone deposits, which is opened by producing and injection wells. Initially, the coolant is injected into the injection well at a high speed so that a thermal connection is established between the wells and a heated permeable (steam) chamber is created.

At the boundary of the chamber, steam condenses and heat is transferred through conduction to colder surrounding areas. The temperature of the oil near the chamber rises, and it flows down along with the hot steam condensate. Oil is continuously removed in the area below the steam chamber.

The coolant contributes to the expansion of the heated permeable chamber with a continuous flow of oil into the producing well.

The production of highly viscous mobile oil is carried out through a production well. Steam is used as a heat carrier.

Oil production is regulated so that separate flows of oil and water are maintained and excessive steam breakthrough is eliminated.

Various well configurations are used to implement the present invention. The following elements are common to all configurations: a) a production well is used that “continues” through the tar sand bed or as a horizontal well, or by creating a fracture (or a combination of both); b) “thermal connection” between injection and production wells is established before the start of oil production. Double concentric tubing strings are placed inside the casing. The inner tubing string is located in the surrounding outer tubing of larger diameter.

The flow rates of water and heavy oil are carefully monitored to ensure optimal oil production without excessive steam breakthrough.

The disadvantage of this method is the low production efficiency of highly viscous oil due to the lack of control of the uniformity of heating of the steam chamber by thermal exposure.

The closest in technical essence is the method of development of high-viscosity oil deposits (patent RU No. 2379494, IPC ЕВВ 43/24, published on January 20, 2010), including pairs of horizontal injection and production wells, the horizontal sections of which are placed parallel to each other in a vertical the planes of the reservoir, equipped with a tubing string, allowing simultaneous injection of coolant and selection of products, injection of coolant, heating of the reservoir with the creation of a steam chamber, selection of products through the production well tubing reagent and monitoring of technological parameters of the formation (temperature distribution along the filter portion of the wellbore) and the well (fluid temperature and pressure at the wellhead and at the pump intake, fluid sampling rate and steam injection rate), simultaneously during the production sampling periodically (2- 3 times a week) determine the mineralization of the water taken along the way, analyze the effect of changes in the mineralization of the water taken along on the uniformity of heating of the steam chamber and, taking into account the changes in mineralization, we select water, the steam chamber is uniformly heated by adjusting the coolant injection mode or selecting well products until a stable mineralization value of the water taken along the way is achieved.

However, this method allows you to adjust the uniformity of heating within one pair of wells and does not take into account the mutual influence of the expanding steam chambers of neighboring pairs of wells.

The objective of the proposed solution is to increase the development efficiency of a highly viscous oil deposit by ensuring uniform distribution of steam chambers by regulating the modes of coolant injection and selection of high viscosity oil, aligning the distribution profile of steam chambers, and also by determining the direction of propagation of steam chambers.

The problem is solved by the method of developing a highly viscous oil reservoir using at least two pairs of continuous horizontal injection and production wells, the horizontal sections of which are placed parallel to one another, including the injection of coolant through the upper horizontal injection wells, the simultaneous selection of highly viscous oil through the lower horizontal production wells and regulation injection and selection of high-viscosity oil.

New is that on each pair of horizontal wells located at a distance of 100 to 150 m from each other, periodically, 1-2 times a month, the viscosity of the selected high-viscosity oil is determined, pairs of horizontal wells are selected, the viscosity viscosity of which are different from each other by 10% or more, analyze the effect of changes in the viscosity of high-viscosity oil pairs of wells on the uniformity of heating of steam chambers, regulate the mode of pumping coolant and product selection until a uniform distribution of steam O chambers are flow rate monitoring viscosity and high viscosity oil.

Figure 1, 2 presents the layout of pairs of single well and double well wells, respectively.

Figure 3 - arrangement of two pairs of wells.

Figure 4 shows the dynamics of changes in the viscosity of high-viscosity oil on the example of a pair of wells No. 1 and a pair of wells No. 2.

Figure 5 shows the dynamics of changes in the flow rate of highly viscous oil on the example of a pair of wells No. 1.

SUMMARY OF THE INVENTION

The development of a high-viscosity oil reservoir by traditional methods without the use of heat is characterized by low oil recovery rates (5-15%). Significantly increase the efficiency of oil displacement (3-4 times) is possible through the use of thermal methods of stimulation. The flow of coolant into the reservoir reduces the viscosity of the oil and allows you to remove it to the surface using conventional technical means.

One of the most effective thermal methods for producing highly viscous oil is the use of a pair of horizontal injection and production wells, the horizontal sections of which are placed parallel to one another in the same vertical plane of the reservoir, equipped with a tubing string that allows simultaneous injection of a coolant (for example, steam) and selection of products - high-viscosity oil, pumping coolant, warming the reservoir with the creation of a steam chamber, selection high-viscosity oil production well via tubing and control of the technological parameters of the formation and the borehole.

The layout of the wells and the location of the tubing shown in Fig. 1 (one pair of single-well wells), Fig. 2 (one pair of double-well wells) include production 1 and injection 2 wells, revealing the reservoir 3. Wells are drilled so that the horizontal section 4 of well 2 is located above the horizontal section 5 of well 1 in one vertical plane at a distance of 5 to 7 m. Well 2 is used to pump coolant into reservoir 3 and create a steam chamber, well 1 is used to produce highly viscous oil. The wells are equipped with tubing strings 6. Well 1 includes pumps 7 for lifting highly viscous oil to the surface. The process of steam and thermal exposure begins with the preheating stage, during which the steam is circulated in the production and injection wells. Due to the conductive heat transfer, the cross-hole zone of the reservoir (the zone between the producing and injection wells) is heated, while the viscosity of high-viscosity oil decreases, its thermal expansion occurs, and mobility increases. After establishing a hydrodynamic connection between the producing and injection wells, the steam injection into the producing well is stopped, and steam is continued to be injected into the injection well, which, due to the difference in density, tends to the upper part of the reservoir, creating a larger vapor chamber. At the interface between the steam chamber and cold oil-saturated thicknesses, a heat exchange process constantly occurs, as a result of which the heated, highly viscous oil is removed to the surface.

In the method for developing a highly viscous oil reservoir, at least two pairs of injection and producing horizontal wells are used. The pairs of wells located at a distance of 100 to 150 m from each other are determined. During the selection of high-viscosity oil, periodically, 1-2 times a month, high-viscosity oil is sampled, then the oil samples are dehydrated and the viscosity of the produced high-viscosity oil is analyzed. Then choose pairs of horizontal wells, the viscosity of high-viscosity oil which differ from each other by 10% or more (figure 3), analyze the effect of changes in high-viscosity oil pairs of wells on the uniformity of heating of steam chambers. Due to the zonal heterogeneity of the developed reservoir, the viscosity of high-viscosity oil in one pair of wells differs from the viscosity in another pair of wells and has its tendency to change. To increase the efficiency of the production of high-viscosity oil on each pair of wells, the operating modes are regulated by changing the volume and proportions of the injected steam and the produced high-viscosity oil.

A change (decrease or increase) in the viscosity of high-viscosity oil in one of the pairs of wells by 10% or more indicates that the steam chamber, expanding, reached a zone characterized by a viscosity of oil that differs from the original. Comparing the values of the changed viscosity of high-viscosity oil in one pair of wells with trends in the viscosity of oil in other pairs of wells, we can conclude the direction of propagation (movement) of the steam chamber. Uneven expansion of the steam chamber can lead to its premature breakthrough to other pairs of wells and reduce the efficiency of high-viscosity oil production, reducing the contact area of the steam chamber with oil-saturated rock. Assume that initially the viscosity of high viscosity oil of a pair of wells No. 1 is 10% or more higher than the viscosity of high viscosity oil of a neighboring pair of wells No. 2 (Fig. 3). A decrease in the viscosity of high-viscosity oil in a pair of wells No. 1 by 10% or more suggests that the steam chamber of a pair of wells No. 2, expanding, significantly approached the drainage zone of a pair of wells No. 1. To reduce the uneven distribution of the steam chamber, it is necessary to reduce the amount of steam injected into a pair of wells No. 2 and to reduce the selection of highly viscous oil in a pair of wells No. 1. In this case, the growth rate of the steam chamber of a pair of wells No. 2 will decrease, which will allow to maintain the oil flow rate of a pair of wells No. 1. An increase in the viscosity of high-viscosity oil of a pair of wells No. 2 by 10% or more suggests that the steam chamber of a pair of wells No. 1, expanding, approached the drainage zone of a pair of wells No. 2. To reduce the uneven distribution of the steam chamber, it is necessary to reduce the amount of steam injected into a pair of wells No. 1 and to reduce the selection of highly viscous oil in a pair of wells No. 2. In this case, the growth rate of the steam chamber of a pair of wells No. 1 will decrease, which will allow to maintain the oil flow rate of a pair of wells No. 2.

After ensuring uniform distribution of the steam chambers, the flow rate and viscosity of high-viscosity oil are monitored.

Case Studies

Example 1

In the experimental section of a highly viscous oil deposit (Ashalchinskoye field), located at a depth of 90 m, it is represented by heterogeneous formations with a thickness of 20-30 m with a temperature of 8 ° C, a pressure of 0.5 MPa, an oil saturation of 0.70 units, a porosity of 30%, with a permeability of 0.265 μm, with highly viscous oil having a density of 956 kg / m and a viscosity of more than 3,000 mPa · s, 2 pairs of horizontal wells are identified: pair No. 1, pair No. 2 (Fig. 3) located at a distance of 100 m from each other. The viscosity of high viscosity oil of a pair of wells No. 1 initially amounted to 5360-5920 mPa · s, the viscosity of high viscosity oil of a pair of wells No. 2 initially amounted to 3420-3920 MPa · s (26.9-42.2% lower than the viscosity of high viscosity oil of a pair of wells No. 1) . Each of the pairs of wells consists of a pair of continuous horizontal wells: injection and production wells, the horizontal sections of which are parallel to each other in the same vertical plane of the reservoir. Prior to the development of producing horizontal wells, the interwell zone was heated by simultaneously circulating steam in each of these wells. Steam injection was carried out through the upper injection well and the production of high-viscosity oil through the lower production well.

From the beginning of development for the period from June 4, 2009 to December 3, 2009, periodically, 1 - 2 times a month, the viscosity of the produced high-viscosity oil was determined. Analysis of the dynamics of changes in the properties of high-viscosity oil of a pair of wells No. 1 in the period from June 4, 2009 to September 10, 2009 showed that there is a gradual increase in the viscosity of high-viscosity oil (Fig. 4). The viscosity value of high-viscosity oil on September 10, 2009 was 6120 MPa · s. The next sampling was performed on September 24, 2009, an analysis of the viscosity of high-viscosity oil showed that the viscosity of high-viscosity oil sharply decreased and amounted to 4260 MPa · s, which is 30.4% less than the previous value.

At the same time (from June 4, 2009 to December 3, 2009) the viscosity of high-viscosity oil, taken from a pair of wells No. 2. during the whole process of vapor-gravity impact on the formation gradually increased. The value of high-viscosity oil viscosity on September 24, 2009 was 3960 MPa · s. This suggests that the steam chambers of both pairs of wells unevenly expand to the sides, propagate in the direction towards each other, and at the time of a sharp decrease in the viscosity of high-viscosity oil of a pair of wells No. 1, part of the high-viscosity oil from the region of a pair of wells No. 2 enters the region of a pair of wells No. 1, as evidenced by a decrease in the viscosity of highly viscous oil produced from a pair of wells No. 1. This, in turn, led to a decrease in the area of coverage of the oil-saturated zone by heat and steam and, as a result, to a decrease in the efficiency of production of high-viscosity oil. To prevent the steam chamber from breaking through a pair of wells No. 2 to an adjacent pair of wells No. 1, aligning the distribution profile of the steam chamber, the steam injection into the injection well of couple No. 2 was gradually reduced (starting from 10 to 35%) and the selection of high-viscosity oil from the producing well of couple No. 2 was reduced. 1 (starting from 5 to 20%). The growth rate of the steam chamber of a pair of wells No. 2 decreased, as evidenced by the level of flow rate of a pair of wells No. 1 (figure 5). The average production rate of high viscous oil produced by a pair of wells No. 2 amounted to 30.1 tons / day. Then they continued to monitor the viscosity and flow rate of high-viscosity oil, regulate the injection and production selection regimes until a uniform distribution of steam chambers was achieved.

The proposed method for developing a highly viscous oil deposit allows to increase the efficiency of developing a highly viscous oil deposit due to the uniform formation of steam chambers and heating of the formation by heat exposure by regulating the modes of coolant injection and product selection.

Claims (1)

A method for developing a highly viscous oil reservoir using at least two pairs of continuous horizontal injection and production wells, the horizontal sections of which are placed parallel to one another, including the injection of coolant through the upper horizontal injection wells, the simultaneous selection of highly viscous oil through the lower horizontal production wells and adjusting the injection mode and selection of high viscosity oil, characterized in that on each pair of horizontal wells located at a distance From 100 to 150 m apart, periodically, 1-2 times a month, the viscosity of the selected high-viscosity oil is determined, pairs of horizontal wells are selected, the high-viscosity oil viscosity indices of which differ from each other by 10% or more, the effect of changes in high-viscosity viscosity is analyzed oil pairs of wells for uniform heating of the steam chambers, regulate the mode of coolant injection and product selection until a uniform distribution of the steam chambers is achieved, monitor the flow rate and viscosity of high-viscosity oil.

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