RU2741978C1 - Method for rapid isolation of absorbing zone in well with high-flow inter-compartment flow from superhigh stratum saturated with strong brines, and packer equipment for implementation thereof - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industries.

SUBSTANCE: invention relates to oil and gas industry, in particular, to methods of isolation of zone of hydraulic fracturing of reservoir and catastrophic absorption in conditions of inter-zone overflow from fossil material to absorbing stratum. To implement the method for rapid isolation of the absorbing zone in the well, the depth of the roof of the absorbing formation and the depth of the absorption zone are determined from geophysical survey data. Drillable packer equipment is lowered into the well on a geophysical cable with installed load for 20 kN disconnection in excess of its own weight. When lowering below the interval of high-pressure refractory formation due to creation of additional load on the booster unit due to pressure drop between developing and absorbing formation cable disconnects from packer equipment. Packer equipment, carried away by liquid flow, is accelerated and reaches bottomhole, where at impact of head part of weighted tapered weight with booster unit to bottom face, transformable packer is deformed due to speed of movement along well bore and blocks flow of liquid into absorbing formation. Water-swelling packer additionally isolates the absorption zone, and over time, the salt precipitated from the brine additionally isolates the absorbing formation, providing further transition to works on insulation of the high-pressure refractory formation by the casing string. Packer equipment comprises transformable packer with sealing for geophysical cable, water-swellable packer, weighting cone with acceleration unit equipped with tail unit. Packers are rigidly interconnected by a rod. Weighted taper with acceleration unit is connected with transformable packer by flexible coupling.

EFFECT: achieving the technical result - bringing the well to the design bottomhole and improving the reliability of the open wellbore attachment by the casing string and providing accident-free oil and gas recovery.

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Description

The invention relates to the oil and gas industry, in particular to the technology for the construction of deep wells, oil and gas production, in particular, to methods of fast isolation of the fracture zone and catastrophic loss in conditions of interstratal flow from the inter-salt brine to the absorbing formation.

A feature of the geological structure of some hydrocarbon deposits is the presence of abnormally conductive cavernous-fractured karst-combined inter-salt reservoirs [Lucia F. J. Construction of a geological and hydrodynamic model of a carbonate reservoir: an integrated approach. - M. - Izhevsk: Research Center "Regular and Chaotic Dynamics". Izhevsk Institute of Comp. Issled., 2010, - 384 p.] with abnormally high reservoir pressures (AHPP) of fluids - brine, oil and gas in the middle part of the sedimentary cover section (for example, one of the oil and gas condensate fields of the Lena-Tunguska oil and gas province) at depths of 1300-2000 m, opening by the bottom of the well of high-rate (up to 5-8 thousand m ³ / day) brine-producing cavernous-fractured reservoirs makes it difficult or excludes drilling of wells to the target underlying horizons (depths of 3300-3600 m) with hydrocarbon (HC) saturation and abnormally low reservoir pressure (ANPD). Continuing drilling without overlapping inter-salt high-pressure productive formations is impossible due to incompatibility of drilling conditions. Intersalt AVPD band characterized by very high reservoir pressures (more than 40 MPa at depths of 1300-2000 meters vertically) and a maximum saturation saturated brine (density up to 1450 kg / m ^3). At the same time, according to the geo-field data, inter-salt reservoirs are localized in the geological section, and therefore anomalously high reservoir pressure (AHPP) of brine is typical in the local interval of the section - in a specific inter-salt reservoir, and downstream in the section in reservoirs, reservoir (pore) pressure close to normal hydrostatic [Vakhromeev AG, Sverkunov SA, Ilyin AI, Pospeev AV. Gorlov I.V. Mining and geological conditions for drilling brine-producing zones with anomalously high reservoir pressure in natural reservoirs of the Cambrian at the Kovykta gas condensate field // Bulletin of the Siberian Branch of the Earth Sciences Section of the Russian Academy of Natural Sciences, 2016. - No. 2 (55). - S. 74-87].

When a brine-producing reservoir with abnormal pressure of brine is opened, the continuation of drilling a well with heavy mud with a density of more than 2420 kg / m ³ , or with back pressure when drilling with controlled pressure often leads to spontaneous formation of hydraulic fracturing in the underlying "weak" formations (that is in reservoirs with reservoir (pore) pressure close to hydrostatic). In this case, in the open wellbore between the high-rate gas-producing and absorbing reservoirs, an interstratal cross-flow occurs, which is extremely difficult to eliminate. One of the significant features of such a crossflow is that the zone of an artificial hydraulic fracturing (auto-hydraulic fracturing) at the bottomhole is formed spontaneously. Further, from the moment of the initiation of the auto-hydraulic fracture, the brine-producing inter-salt abnormally high-pressure reservoir maintains pressure (pressure drop - repression) in the open wellbore, which ensures continuous expansion of the area of propagation of the auto-hydraulic fracture from the bottom of the well along the formation, i.e. supports the auto-hydraulic fracturing process in the same way as it is implemented during the planned creation and consolidation of artificial hydraulic fracturing [Usachev P.M. Hydraulic fracturing // M .: Nedra, 1986. - 165 pp.] The second significant feature of such a spontaneous interstratal crossflow in the well in the interval between the brine-producing and absorbing layers is the flow rate of fluid (brine) at the level of several thousand m ³ / day.

Thus, the pressure drop dP (repression between the magnitude of the abnormally high pressure of the brine-producing layer and the magnitude of the pore pressure of the absorbing strata) and the consumption of brine - the natural fluid system, provided by the natural parameters of the brine-producing stratum, form a problem in the drilling cycle - how to reliably isolate the auto-fracturing zone - the catastrophic zone losses, since under conditions of high-rate crossflow it is impossible to qualitatively cement the casing, which is planned to cover brine-producing fractured reservoirs and absorbing inter-salt formations.

At the same time, isolation of the overlying high-pressure brine formation without cutting off the underlying absorbing formation at the bottomhole during interstratal cross-flow is impossible.

Known (RF patent for invention No. 2018631, E21B 33/138 (1990.01), publication date: 08/30/1994) a tampon for isolating the absorption zone during well drilling, containing a tape-filamentary filler, a drillable load, which is made with the possibility of placing it in the borehole wells in the working position, and the tape-filamentous filler is made in the form of a bundle with the possibility of its expansion in the flow of cement slurry, while one of the ends of the bundle of the tape-filamentary filler is rigidly connected to the load to be drilled.

Known (RF patent for invention 2049909, E21B 33/14 (1995.01), publication date: 12/10/1995) a tampon for isolating the absorption zone during well drilling, containing tape-filamentary fillers of various densities and a load from the material to be drilled, while the fillers contain different sizes tape flaps are made in the form of a bundle, one of the ends of which is rigidly connected to the end part of the load, and fillers with a density of less than 1 g / cm ³ are connected with the central part of the load, and fillers with a density of more than 1 g / cm ³ with the peripheral part of the load.

It is known ("Geophysical methods of researching wells", M: "Nedra", 1983, 591 s, p. 32) the design of a packer containing a transformable housing, and the housing contains a means that prevents the passage of liquid, which is a layer of fibers made of organic polymers and / or fiberglass, the body being made of materials at least slightly soluble in the well fluid.

It is known (RF patent for invention No. 2330931, E21B 33/12 (2006.01), G01V 1/00 (2006.01), publication date: 08/10/2008) a device that performs the function of a packer or a temporary plug, which is a transformable packer that is lowered to a depth installations on pipes or geophysical cable.

The disadvantage of the listed technical solutions of the known tampons and packers of the considered designs should be recognized the complexity of their installation in the well with interstratal crossflow, namely, the occurrence of increased loads on the geophysical cable after passing the developing zone, as a result of which the packer may be disconnected from the geophysical cable before it is put into action. and when using a pipe string, very large one-stage tensile loads can occur - up to 70 tons, and the inability to maintain large pressure drops (repression) between the developing and absorbing formation of 5-15 MPa.

The closest in technical essence to the device is ("Geophysical methods of researching wells", M., "Nedra", 1983, 591 p, p. 550 - a prototype of the device) the design of an explosive drillable packer containing a body transformable by the pressure of powder gases.

The disadvantage of this device is that it can be used in a casing with a consistent inner diameter, and in an open hole the diameter is not maintained due to caverns, its installation is ineffective. Also, the signal to activate the blast packer is carried out through an electrical impulse. When installed in a well with interstratal cross-flow, increased loads on the geophysical cable arise after passing the developing zone, as a result of which the packer may be disconnected from the geophysical cable before it is activated, and when using a pipe string, very large simultaneous tensile loads can occur - up to 70 tons , and the inability to maintain large pressure drops (repression) between the developing and absorbing formation 5-15 MPa. As a result, activation of the blast packer is not possible.

The closest method in technical essence is a method for conducting isolation work in a well (RF patent for invention No. 2414586, E21B 33/13 (2006.01), E21B 33/12 (2006.01), publication date 03/20/2011 - a prototype of the method), containing the descent of the drilled packer on the drill pipe string, unpacking and work to isolate the absorption zone of the underlying and overlying interval.

The disadvantage of this method is that the use of a drillable packer on the drill pipe string when lowering into the interstratal flow zone (above is the high-pressure developing formation, below the absorbing formation) there will be a sharp increase in weight on the hook due to the pressure difference between the developing and absorbing formation more than 10 MPa , the weight gain in the barrel diameter of 295.3 mm can be up to 70 tons to its own. In this case, emergency situations are very likely. Also, this method is quite time-consuming.

The objective of the present invention is to develop an algorithm (sequence of operations) in the well drilling cycle for the purpose of express (fast) temporary isolation of the absorption zone and the resulting high-rate interstratal crossflow, which (the algorithm) will reliably provide the possibility of continuing work on isolating the high-pressure developing formation at the bottomhole, in the future will provide a return to work on the final isolation of the absorbing formation, drilling and completion of the well and further oil and gas production from the underlying formations, as well as the development of the packer equipment used to implement the proposed method.

The essence of the invention is express (fast) temporary isolation of the underlying absorbing formation by installing packer equipment, including two drillable packers with different principles of operation into the wellbore.

EFFECT: bringing the well to the target bottom, reliable casing of the open borehole, and ensuring trouble-free oil and gas production (achieved by simplifying the technology of placing packers in the well).

The technical result is achieved by the proposed method of express isolation of the absorbing zone in the well with a high-rate interstratal crossflow from the overlying high-pressure formation saturated with strong brines, including determining the depth of the absorbing formation top and the depth of the absorption zone according to geophysical studies, lowering the drilled packer equipment into the well on a running tool, when In this case, the drilling of the packer equipment to be drilled is carried out on a geophysical cable with an established disconnection load of 20 kN in excess of its own weight, then when descending below the interval of a high-pressure brine formation due to the creation of an additional load on the upper stage due to the pressure difference between the developing and absorbing formation, the cable is disconnected from the packer equipment , while the packer equipment, carried away by the fluid flow, accelerates and reaches the bottom, where, upon impact of the head part of the weight cone weight, with By the upper block about the bottomhole, the transformable packer is deformed due to the speed of movement along the wellbore and blocks the flow of fluid into the absorbing formation, then the water-swellable packer additionally isolates the absorption zone, and over time, the salt falling out of the brine additionally isolates the absorbing formation, providing a further transition to isolation work high-pressure brine formation with a casing string.

The packer equipment includes a transformable packer with a seal for a geophysical cable, while it additionally contains a water-swellable packer, weighting the cone surcharge with an accelerating block equipped with a tail unit, while the packers are rigidly connected to each other by a rod, and the weighting cone surcharge with an accelerating block is connected to a transformable packer flexible coupling.

The invention is illustrated by drawings, where Fig. 1 shows a general view of the proposed packer equipment for implementing the method.

The packer equipment includes in its layout (Fig. 1): a weighted conical surcharge 1 with a booster block 2 with a tail unit, which serves as a direction for running the packer assembly, including after disconnecting the geophysical cable, flexible coupling 3, transformable packer 4, water-swellable packer 5 , rod 6 connecting transformable 4 and water-swellable 5 packers, sealing 7 for geophysical cable.

FIG. 2 shows a view of the packer equipment after activation at the bottom of the well.

FIG. 3 shows a booster block 2 with a tail unit, which is larger than the diameter of the well 8, made in the upper part of the weighted cone weight 1.

EXAMPLE

As an example, typical conditions are shown when drilling high-pressure high-rate formations saturated with strong brines in one of the oil and gas condensate fields of the Lena-Tunguska oil and gas province (OGP).

Depth of previous casing running 245 mm - 2100 m.

The depth of the high-pressure reservoir is 2150 m.

The pressure in the high-pressure reservoir is 52 MPa (reservoir pressure gradient is 2.42 kg / cm ² per 10 m).

The flow rate of the high-pressure reservoir is 4000 m ³ / day with a depression of 10 MPa. With a depression of 7 MPa, the flow rate is 3000 m ³ / day.

The density of the drilling mud is 1900 kg / m ³ .

When drilling with a 215.9 mm bit at a drilling mud density of 2000 kg / cm ³ with controlled pressure at a depth of 2150 m, a high-pressure productive rock-bearing formation with abnormally high pressure was discovered. Wellhead pressure increased to 9 MPa. When the bottom-hole unit was washed out, the flow of natural brine - brine into the wellbore (density 1400 kg / m ³ ) was recorded with an increase in gas readings up to 5-8%.

Further drilling continued to a depth of 2300 m with controlled pressure with back pressure at the wellhead of 9-10 MPa. Absorption was observed up to 2-3 m ³ / h. The inflow of brine-brine into the well was not recorded.

At the bottom hole of 2300 m by closing the rotary wellhead dock (RHG), the wellhead pressure was increased to 12 MPa, while there was a sharp drop in wellhead pressure to 0, and complete absorption was recorded. The static level in the well dropped to a depth of 50 m (the injectivity pressure of the absorbing formation is approximately 45 MPa). In the well, interstratal crossflow began with a pressure drop between the developing and absorbing formation of 7 MPa. Next, a standard complex of geophysical studies of the well is carried out to determine the depth of the top of the absorbing formation and the depth of the absorption zone according to the data of geophysical studies. According to the geophysical studies of the well, the absorption zone is identified at the bottomhole (depth 2300 m) in the carbonate formation. The top of the carbonate stratum, according to geophysical surveys, is identified at a depth of 2295 m. Or, the depth of the top can also be determined by the drop in mechanical velocity when drilling a halogen-carbonate stratum. The borehole diameter in the carbonate formation is close to the nominal one, since caverns in hard rocks are not filled in, which is optimal for installing a packer assembly. At the same time, the thickness of the carbonate formation (5 m) allows the installation of a packer assembly in this carbonate formation.

In general, the packer equipment is assembled in the form of an arrow with a head in the form of a hunting bullet with a booster block.

The weighting cone surcharge at the head of the assembly plays a centering role and the role of a weighting agent (90% of the weight of the assembly). All elements of the packer assembly are made of easily drillable materials. The weighting cone surcharge can be made of copper, brass and lead alloys.

The flexible hitch is approximately 0.4 m in length.

The length of the packer assembly is determined based on the results of logging of the well to determine the optimal distance between the packers and overlap the lost circulation zone.

The packer equipment is running, including a packer arrangement: transformable 4 and water-swellable 5, on a geophysical cable to a depth of 2150 m. The length of the packer assembly is selected in such a way that it is multiples of the total length of the absorption zone in the bottomhole zone of the well. Further, an increase in the load is recorded (the approximate weight gain at an overpressure of 7 MPa per packer will be about 250 kN), the cable will be disconnected from the packer equipment at a load of more than 20 kN (which is one of the standard values when terminating a geophysical cable 7), then the flow rate ( about 1 m / s) the packer assembly is carried to the bottom. The transformable packer 4 is deformed about the bottom of the well due to the speed of movement in the flow and the subsequent increase in pressure on the packer (7 MPa, which corresponds to the impact force of 250 kN), and overlaps the absorption zone, over time, the water-swellable packer 5 additionally closes the absorption zone, when In this case, the salt falling out of the brine due to the change in thermobaric conditions (in the well relative to the reservoir) additionally isolates the absorbing formation.

Claims (2)

1. The method of express isolation of the absorbing zone in the well with high-rate interstratal crossflow from the overlying high-pressure formation saturated with strong brines, including determining the depth of the top of the absorbing formation and the depth of the absorption zone according to geophysical studies, lowering the drilled packer equipment into the well on a running tool, characterized by the fact that that the descent of the packer equipment to be drilled is carried out on a geophysical cable with an established disconnection load of 20 kN in excess of its own weight, then when descending below the interval of a high-pressure brine formation due to the creation of an additional load on the upper stage due to the pressure difference between the developing and absorbing formation, the cable is disconnected from the packer equipment , at the same time, the packer equipment, carried away by the fluid flow, accelerates and reaches the bottom, where, when the head part of the weighting cone weight with the accelerating block hits the bottom of the transfo The fixed packer, due to the speed of movement along the wellbore, is deformed and blocks the fluid flow into the absorbing formation, then the water-swellable packer additionally isolates the absorption zone, and over time, the salt falling out of the brine additionally isolates the absorbing formation, providing a further transition to work on isolating the high-pressure brine formation with a casing column. 2. Packer equipment, including a transformable packer with a seal for a geophysical cable, characterized in that it additionally contains a water-swellable packer, which makes the conical surcharge heavier with an accelerating block equipped with a tail unit, while the packers are rigidly connected to each other by a rod, and the weighting cone surcharge with an accelerating the block is connected to the transformable packer by a flexible coupling.

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