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53. Деряев А.Р., Аманов М., Деряев С.А.. Вскрытие и освоение многопластовых продуктивных горизонтов методом одновременно-раздельной эксплуатации. // Научный журнал Аспирант и соискатель №5 (119), - М: ООО Издательство Спутник +.2020. - с. 23-30.
4. Деряев А.Р., Гулатаров Х., Оразклычев Г., Еседулаев Р. Рекомендации по комплексному освоению метода одновременно-раздельной эксплуатации на месторождениях западной и восточной части Туркменистана / Сборник статей Института нефти и газа, выпуск 11. - Ашгабат: Туркменская Государственная служба печати. 2015.- с.194-202.
DEVELOPMENT OF WELL DESIGNS FOR THEIR DUAL COMPLETION
Deryaev A.
Candidate of Technical Sciences, Senior Researcher, Scientific Research Institute of Natural Gas of the State Concern „ Turkmengas", Ashgabat, Turkmenistan https://doi.org/10.5281/zenodo.6912986
Abstract
This article describes the development of a well design for dual completion (DC) of multi-layer deposits in order to accelerate the development and increase oil production with the introduction of new technologies and highly efficient equipment. Calculations were made for the development of a well design for DC from the two-year operation of three large horizons, consisting of 7-9 productive layers. As a result, it was determined that the resulting large inflow of oil during the development of these wells proves the success of drilling operations in this area, proving that it is reasonable to choose the right design for dual completion operation of wells.
Keywords: oil and gas phenomenon, conductor, shoe, annular space, borehole, casing string, wellhead, preventer.
The development of the well design begins with the solution of two problems; the determination by calculation of the nominal diameters of the casing strings and the diameters of the rock-breaking tool.
The number of casing strings is determined based on the analysis of the geological section and the location of the well, the presence of areas where drilling is associated with great complications, analysis of changes in the coefficients of anomalous reservoir pressure and absorption indices, as well as accumulated practical experience of well wiring.
The depth of descent of each casing string is specified in such a way that its lower end is in the range of stable monolithic weakly permeable rocks, and that it completely overlaps the intervals of weak rocks in which hydraulic fracturing can occur when opening zones of abnormally high reservoir pressures in the underlying interval [1].
The diameters of the bits, the diameters of the casing columns, the depth of transition from a larger diameter of the well to a smaller one, the depth of descent of the casing columns, the height of the cement mortar behind the casing columns constitute the concept of the well design. The depth of the conductor's descent is determined by the requirement of fastening the upper unstable deposits and isolation of the upper aquifers or absorbing horizons.
When drilling oil and gas fields with high reservoir pressure, it often becomes necessary to install preventers at the mouth of the conductor, then the depth of the installation of the conductor's shoe is calculated from the condition of preventing hydraulic fracturing during the elimination of oil and gas occurrences according to the formula (1).
H = 100XPw + Pwllyegrad-Yf (1)
The length of the conductor and the height of its cementing are chosen in such a way that it is strong enough and can reliably withstand the forces that may arise when the preventer is closed under the influence of the pressure of productive layers. The possibility of a gas breakthrough from the well through the annular space or through cracks connecting the borehole to the surface should also be excluded.
To select the number of intermediate technical columns and the depth of their descent, a combined graph of changes in reservoir pressure, hydraulic fracturing pressure and hydrostatic pressure of the drilling fluid column is constructed in the coordinates "depth is equivalent to the pressure gradient".
Hydraulic fracturing pressure is determined by the formula (2).
Pfrac. = 0,0083H + 0,66 Pres ; (2)
In the intervals of occurrence of rocks in which a violation of the borehole zone of the well is possible, where the density of the drilling fluid is selected taking into account the rock pressure, instead of reservoir pressure, rock pressure is applied to the combined graph.
The zones of compatible drilling conditions are the zones of attachment of wells by casing strings, their number corresponds to the number of casing strings.
The compatibility of drilling conditions is understood as such a combination when the created parameters of the technological processes of drilling the underlying interval of the well will not cause complications
in the drilled overlying interval, if the latter is not fixed by the casing.
The diameter of the drill bits for the selected casing string is determined by the required borehole between the column and the wall of the well. The size of the borehole depends on the diameter and type of connections of the casing pipes and the profile of the well, the complexity of geological conditions, hydrodynamic pressures during drilling and fixing the interval, the exit from under the shoe of the previous column [2]. The
To select the dia
size of the borehole between the casing and the wall of the well is chosen based on the analysis of the experience of drilling and fixing wells in this area and in similar geological conditions of other neighboring fields or according to the results of specially commissioned research work when drilling support wells in this area. If such data are not available, then when choosing bit diameters, you can use the following recommendations in Table 1.
Table 1.
eter of drill bits
Casing pipe diameter, mm 114-127 140-168 178-194 219-245 273-299 324-351 377-426
Borehole, mm 7-10 10-15 15-20 20-25 25-35 30-40 40-50
Based on the parameters of reservoir pressures at the corresponding depths, calculations were made separately for wells №№.37, 200 and 156 of the values of the equivalents of reservoir pressure gradients according to the formula (3):
Pgrad.res = Pres / 0,01 X H; (3)
Based on the "Safety rules in the oil and gas industry", we find the value of the hydrostatic pressure of drilling fluid for wells №№ 37, 156 and 200.
The minimum excess of the hydrostatic pressure of the drilling fluid column relative to the roof of the formation being opened is shown in Table 2.
The hydraulic fracturing pressure coefficient is determined by the formula (4).
Kfree. = Phydr./ 0,01 X H'> (4)
Based on the calculation results, a combined pressure graph and calculation of the wellbore trajectory were constructed and the following designs were selected.
Table 2.
lYIinimum excess of the hydrostatic pressure of the drilling fluid column relative to the roof of the __formation being opened_
Well depth Minimum excess of the hydrostatic pressure of the drilling fluid over the reservoir (repression), kgf/cm2
(interval), m for oil-saturated For gas-bearing, gas-condensate formations and for-
reservoirs mations in unexplored intervals of exploration wells
<1000 10,0 15,0
1001 - 2500 15,0 20,0
2501 - 4500 20,0 22,5
>4501 25,0 27,0
For the correct selection of the downhole design of directional and horizontal wells, it is necessary to study the lithological and physical characteristics of deposits-reservoir properties of productive layers (porosity, permeability), mineralogical composition, power, conditions of saturation with oil, physical and mechanical properties of rocks [3].
Previously, the following well design was used for drilling wells at the North Goturdepe field.
Conductor 0 426 mm - 200 m,
I technical column 0324 mm-1600 m
II technical column 0244.5 mm - 3600 m
The production column 0139.7mm is 4000-4500 m. depending on the layers being opened according to the project.
In order to conduct research on our scientific work and in order to select the design of wells for dual completion of several productive formations on one well, a thorough study of previously drilled wells was carried out and new types of well designs were selected with a full analysis of geological and geophysical materials.
When choosing and justifying the design of the well № 37 North Goturdepe, the requirements of the "Safety Rules in the Oil and Gas Industry", the Regulations for calculating intermediate columns when Drilling wells on the areas of the State Concern «Turk-menneft» were taken into account and geological and technical information on previously drilled wells on the North Goturdepe area was used.
The choice of the well design was carried out in accordance with the intervals of compatibility of the well section according to the mining and geological
drilling conditions, based on the forecast curves of reservoir pressure of rock rupture, and the following design was justified.
- the shaft direction 0720 mm descends to a depth of 10 m, is fixed with butobeton.
- the elongated direction of 0530 mm descends to a depth of 30 m, in order to overlap unstable, sandy-clay deposits and prevent erosion of the wellhead when drilling under the conductor. The height of the cement lifting is up to the wellhead.
The conductor 0426 mm descends to a depth of 594 m, provides overlap of the upper part of unstable
sandy-clay quaternary deposits, isolation of the borehole from hydrostatically connected waters with the surface and installation of anti-blowout equipment.
The technical column 0324 mm descends to a depth of 2781 meters to overlap the swelling and collapse of the "black clays" of the Absheron tier and reduce the interval of the open hole when drilling for the second technical column 0244.5 mm, is equipped with anti-blowout equipment and to ensure effective well management in case of possible manifestations. The descent of the 0324mm technical column is carried out in two sections. The head of the I section is installed in a stable part of the open hole section, in the range of 1700-2300 meters with logging adjustments. The height of the cement rise behind the column is up to the wellhead.
The descent of the technical column with a diameter of 0244.5 mm is carried out to a depth of 4761 meters, in order to prevent the absorption of drilling fluid with a density of 2.08g/cm3 and the tack of the drilling tool under the influence of pressure drop, as well as effective well management during manifestations using blowout equipment. The descent of the 0244.5 mm technical column is carried out in two sections, and the head of the I section is installed with an approach of 50100 meters into the 0324 mm technical column.
The descent of the operational filter shank 0177.8 mm is carried out to a depth of 4906 meters along the hole (the length of the shank is 4691m-4906m), by installing a suspension device for 50-100 meters inside the casing 0244.5 mm in order to overlap productive horizons.
At borehole №156 North Goturdepe, the following design was chosen based on a combined pressure graph and calculation of the borehole trajectory.
- the shaft direction 0720 mm descends to a depth of 10 m, is fixed with butobeton.
- the elongated direction of 0630 mm descends to a depth of 30 m, in order to overlap unstable, sandy-clay deposits and prevent erosion of the wellhead when drilling under the conductor. The height of the cement lifting is up to the wellhead.
The conductor 0426 mm descends to a depth of 398 m, provides overlap of the upper part of unstable sandy-clay quaternary deposits, isolation of the borehole from hydrostatically connected waters with the surface and installation of anti-blowout equipment.
The technical column 0324 mm descends to a depth of 1999 meters to cover the swelling and collapse of "black clays", is equipped with anti-blowout equipment and provides effective well management in case of possible manifestations. The height of the cement rise behind the column is up to the wellhead.
The descent of a technical column with a diameter of 0244.5 mm is carried out to a depth of 4156 meters, into the roofing part of the productive horizon IXd+e e with an adjustment according to logging data. The shoe of the technical column is installed in clay deposits. The casing 0244.5 mm column was selected according to calculations for the perception of all loads arising during drilling and operation of wells. The height of the cement rise behind the column is up to the wellhead.
The descent of the operational slot shank - filter 0139.7 mm, is carried out to a depth of 4298.5 meters (the length of the shank is 4147-4298.5 meters), with the installation of a suspension device for 50-100 meters inside the casing 0244.5 mm. The descent of the slit shank - filter 0139.7 mm combination with casing pipes is carried out in order to attach the filter to the wall of the well and isolate productive layers from others. The fastening is made by special expansion packers installed as part of the descent slot shank - filter 0139.7mm [4].
At well №156 North Goturdepe, in order to dual completion several productive horizons separately, the depth of descent of the second technical column was increased by 0244.5 mm for fixing the upper productive horizons and the lower horizons with special filters without cementing in the form of a shank.
According to well-known schemes, wells with directional finishing filter without cementing in productive zones has the following advantages:
- simple mounting technology;
- the bottom-hole zone of the productive formation is not polluted with cement;
- ensures the safety of the hole;
- it is possible to carry out work on cleaning the
hole.
For wells №. 37 and №. 200 of the Northern Goturdepe, in order to dual completion several productive horizons separately, the depth of descent of the second technical column was increased by 0244.5 mm for fixing the upper productive horizons, and the lower horizons by casing columns 0139.7 mm with cementing in the form of a shank.
According to the schemes of the well ending in the form of a shank with full cementation in productive zones, there are the following advantages:
- to use the development of the technology of exploration, cementing, secondary opening and development of the well;
- to ensure the overlap of the zones of reservoir water intake and the tightness of the inclined part of the hole;
- to operate overlapping collectors.
References:
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