RU2079639C1 - Method of development of oil-gas-condensate deposits - Google Patents

Abstract

FIELD: oil and gas producing industry. SUBSTANCE: drilled in ring-shaped manner over periphery of oil-bearing pool is a row of deep bypass wells opening the zone of superhydrostatic pressures. Formed with the help of combined operation of bypass wells is thermal gas-water billow moving to depression zone, i.e., to developed pool. When oil and then, also gas-condensate mixture are with drawn from development wells, the total volume of producing pool is reduced. But owing to continued regulated bypass of waters from zone of super hydrostatic pressure and maintenance of thermal gas-water billow, reservoir freed from hydrocarbons is constantly replenished with gas-water mixture. This compensates the pressure depression and intensifies motion of hydrocarbon fluids to development wells. EFFECT: higher degree of recovery of hydrocarbons from oil-gas-condensate deposit, particular, in the presence of permafrost rocks and arid (waterless) zones. 2 dwg

Description

 The invention relates to the oil and gas industry and can be used in the development of massive, formation-massive, oil and gas, gas condensate and gas deposits while maintaining reservoir pressure through the use of a deep autonomous water pressure system.

There is a method of developing multilayer oil fields located within the area of the underlying reservoir with terminal waters, which consists in displacing oil from the reservoir by passing into it overlying terminal water and extracting oil to the surface and maintaining pressure in the reservoir by pumping it from the water surface [ 1]
The disadvantage of this method of developing an oil field is the presence of an additional source of surface water and the construction of an expensive complex of objects of the reservoir pressure maintenance system (RPM), the impossibility of its implementation in the permafrost zone.

There is also known a method of developing an oil field, taken as a prototype, which consists in the fact that, in order to increase the hydrodynamic pressure in an oil and gas saturated formation, it is connected to a hydrodynamically connected underlying water reservoir, the pressure of which exceeds the pressure of the oil reservoir [2]
The disadvantage of this method, taken by us as a prototype, is the drilling of water supply wells directly into the oil content circuit, which can lead to the rupture of deposits into disparate areas and the formation of cones of watering in areas of production wells and, as a result, losses of hydrocarbon materials in its jamming zones, except In addition, natural overflow occurs in the connection zones with the operational ones with a parallel decrease in pressure.

 The objective of the invention is to increase the degree of hydrocarbon recovery of a gas-oil-condensate field in the presence of permafrost and arid (anhydrous) zones.

 The problem is solved in that in the method of developing an oil and gas condensate field (OGCF), which includes the drilling of bypass and production wells, followed by production through the production wells of hydrocarbon raw materials while maintaining pressure in the developed reservoir by transferring produced water from the underlying horizon to the overlying drilling of bypass wells, beyond the oil path to the depths, revealing the autonomous zone of superhydrostatic pressures (GHSD) and create a mobile regulation gas-shaft legal for trade on the contour of the hydrocarbon oil bearing reservoir formation by controlled bypass thermal gas-saturated water through the drilled hole of the bypass sverhgidrostaticheskih pressure zone (AADT) under an oil-bearing zone developed field. With the subsequent use of bypass wells as production wells in the development of the overlying horizon.

Significant differences of the claimed invention are the following:
bypass wells are drilled beyond the oil content circuit to depths revealing a superhydrostatic pressure zone (GHSD);
create a movable adjustable gas-water shaft on the oil-bearing profile of a hydrocarbon deposit by means of controlled transfer of reservoir gas-saturated terminal water through drilled bypass wells from the superhydrostatic pressure zone (SGSD) under the oil-bearing zone of the field being developed; with the subsequent use of bypass wells as production wells in the development of the overlying horizon.

 The above significant distinguishing features are unknown to us from the patent and scientific and technical documentation. Together with the known one, it is possible to solve the problem of the invention.

 Based on the foregoing, we believe that the distinguishing features set forth in the claimed invention meet the criterion of "Novelty."

 The above significant distinguishing features clearly do not follow from the known technical level and in this regard meet the criterion of "Inventive step".

 To implement the development method, the domestic industry produces all the necessary equipment and the use of the invention does not present any particular difficulties. In accordance with this, we believe that the invention also meets the criterion of "Industrial applicability".

 The claimed method is as follows. Figure 1 shows the technology for the development of oil and gas condensate deposits; figure 2 is a bypass well in the marginal zone of the oil and gas condensate field.

 The method of developing oil and gas condensate deposits is made in the following sequence.

 Along the perimeter of the oil part of the deposit (see Fig. 1), a series of deep bypass wells 1, opening the zone of superhydrostatic pressures (SGSD), are drilled annularly in the marginal zone, each of these wells 1 has two perforation intervals (filters): the top 2 in a high-capacity aquifer deposits below the oil-water contact (BHC) and lower 3 within the GHSD zone with high-pressure terminal gas-saturated waters 4. The latter through the filter 3 enter the well using a special isolation-control system (in FIG. Then, they are passed through filter 2 into a high-capacity reservoir containing a hydrocarbon reservoir. Here, below the OWC along the contour of the deposit, partial degassing of deep water occurs and a thermal gas-water shaft 5 is formed with a higher temperature than in the deposit.

 With the help of collaboration, the bypass hole rings 1 form a thermal gas-water shaft 5 advancing into the depression zone, that is, towards the developed deposit. The creation of such a shaft provides long-term maintenance of reservoir pressure in the oil 6 and gas condensate 7 parts of the reservoir. An increase in the temperature at the oil-water contact (WOC) and gas released from the water reduce the viscosity of the oil, increase its mobility and the degree of extraction without reducing the pressure in the gas-condensate part of the reservoir (gas cap). Excess methane gas from the transfer water can significantly increase the recoverable hydrocarbon reserves from the reservoir. During the selection of oil, and then the gas-condensate mixture from production wells 8 and 9, the total volume of the productive reservoir decreases, but due to the continued controlled water bypass from the zone (SFS) and the maintenance of the thermal gas-water shaft 5, the reservoir volume freed from hydrocarbons is constantly replenished with the gas-water mixture, which compensates for pressure depression and intensifies the progress of hydrocarbon fluids to production wells 8.

 The placement of bypass wells 1 along the perimeter of the oil reservoir significantly reduces the likelihood of a rupture of the oil reservoir, the formation of water cones in the areas of production wells 8 and the loss of hydrocarbons.

Example. During the development of an oil and gas condensate field, which includes an oil deposit, gas reserves of 50 billion m ³ , oil 20 million tons and an extensive zone of gas-saturated thermal waters of a similar composition (calcium chloride) with underlying waters of a productive hydrocarbon-containing horizon. In principle, different systems for the development of oil and gas condensate fields are possible.

 An example of calculating the compensation for the selection of hydrocarbons from a deposit due to the bypass of high-pressure thermal carbonated waters from the underlying horizon with superhydrostatic pressure (GHSD).

Initial data:
1. Massive gas condensate reservoir with an oil rim; VNK at a depth of 2000 m. The average pressure in the reservoir is 210 kgf / cm ² , the average temperature is 50 degrees C. The pressure on the KSS 215 kgf / cm ² . The collector is homogeneous, average efficiency porosity 20%
2. Productivity area 360 million m ² gas reserves 50 billion m ³ . Balance oil reserves of 20 million tons, recoverable 6 million tons. The conversion factor for oil is 0.8.

3. Volume in reservoir conditions: gas 238 million m ³ , oil 25 million m ³ . The total volume of steam space occupied by HC 263 million m ³ .

The average annual gas production is 4 billion m ³ . Total reservoir life:
50 • 10 ⁹ : 4 • 10 ⁹ = 12.5 years = 4565 days
5. SGSD horizon at a depth of 4000 m. Regional distribution. It is covered by a powerful clay fluid support. The reservoir is homogeneous, the average effective porosity is 15%. The effective thickness of the aquifers is 150 m. The waters are of the same calcium chloride composition as the bottom waters of the reservoir. The density of water is 1.12 g / cm ³ , gas saturation 4 nm ³ / m ³ . Methane gas. The average reservoir pressure is 600 kgf / cm ² (anomaly coefficient of 1.5), the average temperature is 100 degrees C.

6. Water bypass from the GSSD horizon under the oil-and-gas complex is carried out through 10 wells with a total flow rate of 15 thousand m / ³ days. The average production rate of each well is 1.5 thousand m ³ / day.

 Initially, an oil rim is developed, then the gas condensate reservoir itself. Bypassing water from the GHSD horizon partially compensates for hydrocarbon withdrawals, maintaining pressure in the reservoir, raises the temperature in its lower part by 10-15 degrees C, which increases the mobility of oil, prevents the formation of condensate and paraffin in the reservoir, increases the recovery factor for liquid hydrocarbons and prolongs term of fountain operation.

The total volume of bypassed water is:
ΣQ _in = 15 • 10 ³ • 4565 = 68.5 million m ³ ,
The total volume of gas released from the water (subject to degassing by 50%) is equal to:
ΣQ _g = 4 • 0.5 • 68.5 • 10 ⁶ = 137 million m ³ ,
The volume of this gas in reservoir conditions of the reservoir is about 0.6 million m ³ .

The total volume of pore space occupied by the bypassed water and gas:
68.5 • 10 ⁶ + 0.6 • 10 ⁶ = 69.1 million m ³
Consequently, bypassing water from the GFSD horizon will provide full compensation for oil withdrawals (20 million m ³ provided it is extracted by 80%) and partial compensation for gas withdrawals (69.1 • 10 ⁶ -20 • 10 ⁶ = 49.1 million m ³ ) released in the pore space deposits (or 20-21% of the gas condensate part of the reservoir).

,
где
ΔP депрессия перепуска воды (кгс/см²)
Р_сгсд среднее давление в горизонте СГСД (600 кг/см²)
Р_внк давление на ВНК (215 кгс/см²)
h_b высота столба воды от кровли горизонта СГДС до BHK (2000 m)
ρ_в плотность воды (1,12 г /см³)
Р_п потери на сопротивление при движении воды в скважине (20 кгс/см²)
Отсюда

,
Реализованные упругие запасы воды рассчитываются по формуле:
Q_в.упр=V•m•β_в•ΔP,
где:
V общий объем водоносных пород горизонта СГСД в зоне депрессии (м³);
m эффективная пористость этих пород (0,15);
β_в сжимаемость газонасыщенной воды (4•10^-5 кгс/см²)
ΔP депрессия в перепускных скважинах кгс/см².The bypassed volume of water represents the realized elastic reserves of water released from the GHSD horizon with a decrease in pressure. The average depression in this horizon during bypass is:

,
Where
ΔP depression of water bypass (kgf / cm ² )
R _sgsd average pressure in the horizon sgsd (600 kg / cm ² )
R _VNK pressure on the VNK (215 kgf / cm ² )
h _{b the} height of the water column from the roof of the SRS horizon to BHK (2000 m)
ρ _{in the} density of water (1.12 g / cm ³ )
R _{p the} loss of resistance when moving water in the well (20 kgf / cm ² )
From here

,
Realized elastic water reserves are calculated by the formula:
Q in. _El. = V • m • β _in • ΔP,
Where:
V is the total volume of aquifers of the GHSD horizon in the depression zone (m ³ );
m effective porosity of these rocks (0.15);
β _{in the} compressibility of gas-saturated water (4 • 10 ^-5 kgf / cm ² )
ΔP depression in bypass wells kgf / cm ² .

,
Объем депрессионной воронки на каждой перепускной скважине составляет:
V_скв. 81•10⁹:10=8,1 млрд.м³
Воронка депрессии в горизонте СГСД на каждой скважине имеет в плане форму, близкую к кругу. Депрессия в пределах воронки распределяется неравномерно. Принимая, что ее среднее значение (P=141 кгс/см²) удалено от скважины на расстояние, равное 30% величины радиуса депрессии. Тогда площадь воронки для каждой скважины составит:

,
где
h эффективная толщина пород (150 м)
Отсюда радиус воронки к концу срока эксплуатации залежи достигнет:

,
При периметре залежи 90 км расстояние между скважинами будет равно:
90:10=9 км
Расчет показал, что взаимовлияние перепускных скважин при отборе воды из горизонта СГСД начнется примерно через 1610 суток после начала перепуска воды, т.е. через 4,4 года.Taking the total value of the sold elastic reserves Qb _control. ΣQ _в = 68.5 million m ³ , we determine the total volume of the depression zone in the GHSD horizon:

,
The volume of the depression funnel at each bypass well is:
V _well 81 • 10 ⁹ : 10 = 8.1 billion m ³
The depression funnel in the GHSD horizon at each well has a plan shape close to a circle. Depression within the funnel is not evenly distributed. Assuming that its average value (P = 141 kgf / cm ² ) is removed from the well by a distance equal to 30% of the radius of the depression. Then the area of the funnel for each well will be:

,
Where
h effective rock thickness (150 m)
From here, the radius of the funnel by the end of the life of the reservoir will reach:

,
With the perimeter of the reservoir 90 km, the distance between the wells will be equal to:
90: 10 = 9 km
The calculation showed that the mutual influence of bypass wells during the withdrawal of water from the GHSD horizon will begin approximately 1610 days after the start of the water bypass, i.e. after 4.4 years.

The claimed invention allows us in comparison with the prototype:
increase the degree of hydrocarbon recovery
it is environmentally friendly to develop an oil and gas condensate deposit and reduce the time for producing hydrocarbon deposits, prevent the formation of condensate in the reservoir and increase the temperature of the oil rim;
use natural energy resources without involving extraneous energy sources, which is especially important for permafrost regions and arid zones;
restore hydrocarbon production in underdeveloped fields;
subsequently use the bypass well fund for the new purpose.

Claims (1)

 A method of developing oil and gas condensate fields, including drilling bypass and production wells, followed by production of hydrocarbon feedstocks through production wells, maintaining pressure in the developed deposit by transferring produced water from the underlying horizon to the overlying one, characterized in that the bypass wells are drilled beyond the oil contour to depths that open autonomous zone of superhydrostatic pressures (SGSD), while creating a movable adjustable gas-water shaft at hydrocarbon reservoir oil content by controlled transfer of gas-saturated thermal water through drilled by-pass wells from the SGSD zone to the oil-rich contour zone of the field being developed, followed by the use of bypass wells as production wells in the development of the overlying horizon.

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