RO117724B1 - PROCEDURE FOR EXPLOITATION WITH SUBTERNAL DRAWINGS OF LIQUEFIELDS - Google Patents

Abstract

The invention relates to a process for the exploitation of underground drainage of oil deposits at different stages of exploitation. The underground drainage operation of the oil deposits ensures the inflow of the fluids from the reservoir to the exploitation probe by selecting an operating well (2) dug into the most productive and accessible area of the deposit (1) around which performs a network of multiple probes (4 and 5) located in successive, concentric rows, and at one or more vertically executed levels. After reaching the reservoir (1), the wells (4 and 5) are drilled convergently to the operating well (2), crossing the deposit (1) on a curved path in a drainage zone (3) of the drilling well (2) . The probes (4 and 5) are drilled throughout the deposit (1), and on the segment (b ') above the deposit (1), it is cemented or not up to date, thus creating open underground drains (5') and some closed underground drains (4 ') through which the fluids are located in and to the exploration well (2) both under the action of reservoir energy and gravity.

Description

RO 117724 Β

The invention refers to a process with underground drains for the exploitation of oil fields in various stages of exploitation and which do not have large gas heads, are located in a bedrock over 50m thick, lithologically consisting of limestones, sandstones or consolidated sands with a large surface area, of at least 500m diameter in 5 planes and have a recovery reserve that justifies the financial effort.

A method of exploiting an oil field with a primary gas head is known, which consists of operating on the productive layer through several sets of well holes chosen, at least from two adjacent rows of wells and which cross the layer area, being put in communication with the latter through some perforations made on an interval, 10 having a lower level located relatively much higher than the water-oil contact level. The exploitation is carried out intermittently and being controlled by these sets of well holes that operate alternatively over a period of time, depending on the hydraulic capacity of the productive layer, the flow rate of the wells, the distance between the upper limit of the perforated interval and the gas-oil contact level, the distance between the lower limit of the perforated interval and the water-oil contact level, and the ratio between the densities of the fluids existing in the porous medium of the deposit. While one set of wells is producing, another set or sets of wells adjacent to the producing wells are closed, allowing for a redistribution of fluids during this period of time due to gravitational forces and changing streamlines, with the saturation distribution in the area of the closed wells tending to reach a new equilibrium.

Fluids flow into the well from where they are discharged to the surface using natural energy or additional energy (gas, lift, pumping, etc.), through appropriate special equipment, and then through pipelines they are directed to collection, separation, treatment and storage points.

The number of wells through which the exploitation is carried out is determined mainly by the dimensions of the deposit, the location and distances between them take into account the fact that each well drains fluids from a cylindrical segment of the deposit with a diameter of about 100-200m and a height equivalent to its thickness, called the drainage zone. It therefore follows that on a deposit the exploitation will be carried out with one or more wells, depending on how many different drainage zones can be achieved, without them interfering.

The inflow of fluids is due to the pressure difference that will be achieved between the reservoir and the wellbore, as well as as an effect of gravity, it is also influenced by the degree of opening, respectively by the perforations made in the well column, as well as by a series of parameters of the reservoir such as (rock porosity, existence of cracks, 35 inclination of the collector, fluid viscosity, degree of opening through perforation, etc.); this inflow decreases over time as the pressure in the reservoir decreases, reaching uneconomical flow rates.

The process of exploitation of oil deposits with drains, according to the invention, ensures the inflow of fluids from the deposit to the exploitation well by choosing a 40 exploitation well dug in the most productive area of the deposit, around which a network of several wells is created, placed in successive, concentric rows, executed by drilling with small diameter, vertically to the deposit, from where onwards, the wells are dug in a directed manner, inclined, at 30-70°, converging towards the exploitation well, crossing the deposit on a curved trajectory in a drainage area of the exploitation well, the wells being casingd at 45° throughout the deposit with downpipes provided with slots, and on the segment above the deposit, cementing or not to the surface, thus creating some open underground drains and some closed underground drains, through which the fluids from the deposit flow into and towards the exploitation well, both under the action of reservoir energy and gravity.

RO 117724 B

By applying the oil field drainage exploitation process, according to the invention, the following advantages are obtained: 50

- more efficient use of reservoir energy as well as gravity, which ensures the flow of fluids to the production wells from which they are discharged to the surface;

- uniform decompression of the deposit during exploitation with the extension of the natural eruption period;

- increasing the efficiency of gravity flow throughout the entire exploitation period; 55

- simplification of the system for collecting and transporting surface fluids;

- significant reduction of land areas temporarily or permanently occupied by oil installations; of energy consumption, environmental pollution and the influence of natural, topogeographic and atmospheric factors, as well as of operating errors on the intensity of exploitation; 69

- increased labor productivity and improved management as a result of concentrating extraction in a few exploitation points;

- significant reduction in expenses for the construction of production wells and the system for collecting and separating extracted fluids, as well as for maintaining them in operation; 65

- uniform depletion of the deposit is achieved, the phenomenon of flooding of the production wells with bottom water is delayed, because the pressure difference between the drainage area and the well will be reduced for a long time and therefore water cones will not form.

An example of the process of exploiting oil deposits with drains is given below in connection with Fig. 1 - 3, which represent: 70

- fig. 1, longitudinal section through an oil field exploited by the drain process, according to the invention;

- fig. 2, horizontal plan view of a network of wells dug for the implementation of the oil field exploitation process with drains;

- fig. 3, longitudinal section through an oil field, with construction details 75 of the wells dug for the implementation of the drain exploitation process, according to the invention.

The process of exploitation of oil deposits with drains, according to the invention, comprises the identification and digging in a deposit 1 of an exploitation well 2, in the most productive and accessible position of the deposit, a generally vertical well, with a diameter of 80 large to below the base of the deposit 1. The transversal of the deposit 1 is done with anhydrous fluids, and on a thickness h thereof 3-4 torpedoes are made, at different points to create macrocracks in the store rock. A hole g of the well thus made, is casingd with a column c of downpipes of diameter r of 7-8.5/8 in, with walls δ thick of 8-10 mm, after which it is cemented from the base §i to the surface, then it is perforated on a thickness h with 10 m 85 less in the base or roof if there is active bottom water, respectively significant gas head. Well 2 is equipped with extraction pipes t with a diameter of k 2 3/8 - 3 1/2 in and with an eruption head and possibly with a packer p. Separation, storage, possibly treatment and transport facilities are also located on the surface. Around the exploitation well 2, one or more wells 4 and 5 are drilled in successive, concentric rows, at one or more levels, which are executed through small diameter drillings 3 1/2-5 in, in principle vertically, to the reservoir 1 from where, further, directed digging is carried out, inclined at 30-70°, crossing the reservoir 1 on a curved trajectory to a drainage area 3 with a diameter of approximately 00-200, of the exploitation well 2, at an imaginary point located at about 50 m between the base and the column of the well 2. This crossing is done with anhydrous fluids, and in this segment, 3-4 torpedoes are made at different points to create micro and macro cracks in the store rock. A hole g' of well 4 is cased with a liner I made of pipes of diameter r of 3 1/2-4 in, with walls δ' thick of 6-8 mm, provided with slots with a gap f of 0.3-0.5 mm, which are not cemented in order to obtain a maximum degree of openness. The segment above the reservoir 1 is

Claims (1)

RO 117724 B 100 cements until the day. From the hole g', closed underground drains 4' are thus made, which can be at different depths and in different directions, taking care not to interfere with drainage areas 3', with a diameter d' of about 100m, over large sections. From the well 5, open underground drains 5' are made in the same way as in the well 4. On a segment b' of the hole g' located above the deposit, a column c' is lined, made of pipes of diameter r' of 4-5 in, which 105 column is cemented, after which the cement plug and the plate for opening the open underground drain 5' are milled. These open underground drains 5' are also used for technological interventions such as measurements for monitoring exploitation and are equipped with extraction pipes t', with a diameter k' of 2 3/8-2 7/8 in and an eruption head e', and a recoverable packer p' is used for closure. In the example taken, the hydrodynamic system of the exploitation well 2 on the reservoir block 1 is completed with a network of concentric and convergent drains composed of open underground drains 5' and closed underground drains 4', with the specification that the closed drains 4' are directed into the drainage areas 3 or 3' of the well 2 or the neighboring open underground drains 5, through which the fluids flow under the action of both the reservoir energy and gravity, into and towards the exploitation well 2, where they are extracted to the surface. This creates a concentric network of closed or open underground drains converging in its drainage area, thus creating a common hydrodynamic basin through which the fluids from the deposit flow through its own deposit energy and gravitational energy into the exploitation well from where the drains are discharged to the surface, functioning similarly to the exploitation wells in its own drainage area, as well as similar to flow pipes, thus ensuring the flow of fluids from the entire deposit or from a part of a very large deposit. The practical implementation of the process, according to the invention, can be done with current installations and technologies. 125 Claim Process for exploiting oil deposits with underground drains used to put some deposits into production as well as to intensify the exploitation of some old deposits 130 which consists of digging a network of wells through which fluids are extracted to the surface and which cross the oil deposit in its entirety and are equipped with downpipes provided with slots along the entire height of the deposit with packers, with eruption heads, the crossing of the deposit being done with anhydrous fluids and creating microcracks in the store rock by known operations, characterized in that an exploitation well (2) is chosen dug 135 in the most productive and accessible area of the deposit (1), around which a network of several wells (4 and 5) is created placed in successive, concentric rows, and at one or more levels, executed by drilling with small diameter, vertically to the deposit (1) from where, Next, the wells (4 and 5) are dug in a directed manner, inclined at 30-70°, converging towards the exploitation well (2), crossing the reservoir (1) on a curved trajectory in a drainage area (3) of the exploitation well (2), the wells (4 and 5) being casingd throughout the reservoir (1) with downpipes provided with slots, and on the segment (b') above the reservoir (1) it is cemented or not until the surface, thus creating some open underground drains (5') and some closed underground drains (4'), through which the fluids from the reservoir flow into and towards the exploitation well (2), both under the action of the reservoir energy and gravity, thus creating a common hydrodynamic system in the area affected by the well network. President of the examination committee: Eng. Eane Adrian Examiner: Eng. Comănescu Rom ita