RU2411336C1 - Procedure for well construction - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: procedure for well construction consists in drilling borehole under laminar-flow mode of flush fluid pumping through circular space of well borehole. A conductor is drilled under the laminar-flow mode of flush fluid pumping, further, it is cased and anchored and then the conductor is drilled under turbulent conditions of flush fluid. At occurrence of zones with unstable clay rock at operation under the laminar-flow mode the conductor is cased and cemented. The main borehole is drilled under the turbulent conditions. 5-20 m before a productive horizon of unstable clay rock the borehole drilling is performed under the laminar-flow mode; the well is after-drilled till a design mark, the main borehole of the well is cased and fixed with cement. Also, as flush fluid for the laminar-flow mode there is used fluid of viscosity not exceeding 50 s, while consumption of fluid is maintained not over 16 l/s at drilling with a bit of diametre from 530 to 217 mm, consumption not over 10 l/s at drilling with the bit of diametre from 217 to 155.6 mm and not over 7 l/s at drilling with the bit of diametre from 155.6 to 84 mm.

EFFECT: increased speed of borehole drilling.

1 ex

Description

The invention relates to the oil industry and may find application in the drilling of intervals of formations with unstable rocks.

There is a method of drilling a well with unstable clay rocks without caverning, including deepening the wellbore with a bit in the interval of the formation with unstable clay rocks using viscoplastic flushing fluid in the laminar flow regime in the annular channel of the wellbore (T.N. Bikchurin, I.G. Yusupov, RS Gabidullin. "Study of the influence of various factors on the mode of flow of the drilling fluid through the annular channel of the wellbore." "Oil Management", 2001, No. 4, p. 26).

The method does not provide a guaranteed laminar flow regime in the annular channel of the well when drilling with a bit in the interval of the formation with unstable clay rocks, because the critical speed at which the transition from a laminar flow to a turbulent flow occurs is difficult to control, and in some cases impossible, because in difficult well conditions, the plastic viscosity of the drilling fluid and the dynamic shear stress change.

Closest to the proposed invention in technical essence is a method of sinking unstable clay rocks during the drilling of oil and gas wells, for example shale, comprising deepening the hole with a bit in the interval of the formation with unstable clay rocks using viscoplastic flushing fluid in the laminar flow regime in the annular channel of the borehole . To ensure a guaranteed laminar flow regime in the annular channel of the wellbore, and therefore, penetration with a bit of the above-mentioned interval without caverning, the flow rate of the flushing fluid is selected 20-30% less than the critical flow rate at which the laminar regime changes to turbulent, while the visco-plastic flushing fluid is chosen with the minimum possible filter return (RF patent No. 2256762, publ. July 20, 2005 - prototype).

The disadvantage of this method is the difficulty of determining the critical flow rate and maintaining the laminar flow regime in the annular channel of the wellbore. All this leads to the irreproducibility of the laminar regime, turbulization of the flow of flushing fluid, the appearance of cavern formation and sticking of the drilling tool while drilling the well. In addition, the use of the laminar regime leads to a significant slowdown in the drilling speed of the well.

The proposed invention solves the problem of drilling a well while providing the laminar regime with simple and affordable solutions by introducing restrictions on the properties of the flushing fluid and its pumping mode, as well as increasing the speed of drilling the well.

The problem is solved in that in a method for constructing a well, which includes drilling a well in a laminar mode of pumping flushing fluid for drilling through an annular space of a wellbore, according to the invention, the direction is drilled in a laminar mode of pumping flushing fluid, the direction is drilled and fixed, the conductor is drilled in a turbulent mode of flushing fluid conductor is cased and fixed, the main wellbore is drilled in a turbulent mode, but 5–20 m to the productive horizon with unstable clay rocks go to the laminar regime, drill the well to the design mark, casing and fix the main wellbore, while the flushing fluid for the laminar regime uses a fluid with a nominal viscosity of not more than 50 s, and the fluid flow rate is maintained no more than 16 l / s when drilling with a bit with a diameter of 530 to 217 mm, no more than 10 l / s when drilling with a bit with a diameter of 217 mm to 155.6 mm and no more than 7 l / s when drilling with a bit with a diameter of 155.6 to 84 mm.

When zones with unstable clay rocks appear during conductor drilling, these zones are drilled in a laminar mode.

SUMMARY OF THE INVENTION

The violation of the stability of clay rocks is accompanied, as is known, by complications of the wellbore, collapses and caverns. The presence of caverns, especially between oil and aquifers, reduces the quality of their separation, is the reason for the influx of water during the initial development, as well as the reason for the increase in the percentage of water cut in the formation during the operation of the well. Caverns are mainly formed during the sinking of unstable clay rocks of the Quaternary deposits, Verey, Tula, Bobrikov, Kynovsky, Pashi horizons due to erosion destruction by a turbulent flow of washing fluid. They lead to complications - multiple studies of the trunk and sticking of the drilling tool. So, when attaching the well, the density of the cement in the cavity interval decreases from 1850 to 1300 kg / m ³ . Cement stone from such a solution cannot serve as a reliable support for the annular channel. This leads to serious accidents in the well, accompanied by collapse of the production casing and its sticking, especially in the interval of Kyn clay.

Known methods of drilling wells in a laminar mode are difficult to implement. According to the reproduction of the prototype, the main difficulty is the difficulty of determining the critical flow rate and maintaining the laminar flow regime in the annular channel of the wellbore. All this leads to the irreproducibility of the laminar regime, turbulization of the flow of flushing fluid, the appearance of cavern formation and sticking of the drilling tool while drilling the well. In addition, the use of the laminar regime leads to a significant slowdown in the drilling speed of the well. The proposed invention solves the problem of drilling a well while providing a laminar regime with simple and affordable solutions, as well as increasing the speed of drilling a well. The problem is solved as follows.

First, preparatory work is carried out, namely, that at the drilled well, intervals of unstable clay rocks of the developed oil or gas reservoir are revealed from previously drilled wells or exploratory drilling wells.

The direction is drilled in the laminar mode of pumping the washing liquid, the direction is cased and fixed (cemented annulus).

The need to use the laminar regime when drilling directions is caused by the fact that the upper rocks are unstable, because intercalation of clays and sandstones with lenses of conglomerates and intercalations of limestone takes place. They are weakly cemented and subject to rapid erosion. When drilling in turbulent mode, unplanned complications such as griffins can occur (circulation does not go to the wellhead, but 1-20 m from the wellhead). From erosion, the drilling block may fall underground.

The conductor is drilled in a turbulent mode of flushing fluid. The use of turbulent mode increases the speed of drilling the well as a whole. When zones with unstable clay rocks appear during conductor drilling, they switch to a laminar drilling mode to prevent complications in the form of scree, collapses and to avoid accidents such as sticking of a drilling tool. The conductor is cased and fixed (cemented annulus).

To increase the drilling speed, the main wellbore is drilled in a turbulent mode, but 5-20 m from the productive horizon with unstable clay rocks, they switch to the laminar mode, drill the well to the design mark, casing and fix the main wellbore (cement the annulus).

As a flushing fluid for the laminar regime, a fluid with a nominal viscosity of not more than 50 s is used, and the fluid flow rate is maintained no more than 16 l / s when drilling with a drill bit with a diameter of 530 to 217 mm, no more than 10 l / s when drilling with a drill bit with a diameter of 217 mm up to 155.6 mm and not more than 7 l / s when drilling with a bit with a diameter from 155.6 to 84 mm.

The nominal viscosity of the washing liquid is determined according to RD 39-0147585-232-01 by the time of expiration of the volume of liquid from the funnel with a calibrated hole.

As a result of combining the turbulent and laminar regimes, it is possible to accelerate well construction. Ensuring the laminar regime is achieved by simple and affordable solutions: by limiting the properties of the washing liquid in terms of the nominal viscosity and flow rate when pumping it.

As a washing liquid, clay-chalk, polymer-clay solutions with a density of 1.06-1.60 g / cm ^{3 are used} .

Concrete example

According to previously drilled wells, it is revealed that the intervals of unstable clay rocks of the developed oil or gas deposits begin in the intervals of 1500-1550 m and end in the intervals of 1550-1600 m vertically.

An oil producing well with a depth of 1800 m is being built vertically.

The direction is drilled to a depth of 150 m with a chisel with a diameter of 490 mm in the laminar mode of pumping flushing fluid, the direction is cased and fixed. As a washing liquid, a clay-chalk solution with a density of 1.50 g / cm ³ and with a relative viscosity of 45 s is used. The flow rate of the flushing fluid at the wellhead is maintained at 14 l / s.

The conductor is drilled to a depth of 500 m with a chisel with a diameter of 393.7 mm in a turbulent mode of flushing fluid with a flow rate of 30 l / s at the mouth. Conductor is cased and fixed.

The main wellbore is drilled vertically to a depth of 1800 m with a bit with a diameter of 215.9 mm in turbulent mode with a flow rate of 32 l / s at the mouth of the flushing fluid to a depth of 1490 m vertically. From a depth of 1490 m, i.e. 10 m to the productive horizon with unstable clay rocks, they switch to a laminar regime with a flow rate of 9 l / s at the mouth of the flushing fluid, drill the well to the design level and casing and fix the main wellbore.

As a result of combining the turbulent and laminar regimes, it is possible to accelerate well construction by 40-60% compared with the prototype and reduce the time of well drilling by 4-5 days. The laminar mode of pumping flushing fluid allows you to build a well in conditions of shedding rocks, to eliminate sticking of the drilling tool and to improve the quality of cement stone in the annulus.

Application of the proposed method will allow to solve the problem of drilling a well with a laminar regime and increase the speed of drilling a well.

Claims (1)

A method of constructing a well, including drilling a well in a laminar mode of pumping flushing fluid through the annular space of the wellbore, characterized in that the direction of drilling in a laminar mode of pumping flushing fluid, casing and securing the direction, the conductor is drilled in a turbulent mode of flushing fluid or when zones with unstable clay rocks in laminar mode, conductor is cased and cemented, the main wellbore is drilled in turbulent mode, and 5-20 m before it is productive about the horizon with unstable clay rocks they switch to the laminar regime, drill the well to the design mark, casing and cement the main wellbore with cement, while the flushing fluid for the laminar regime uses a fluid with a nominal viscosity of not more than 50 s, and the fluid flow rate is maintained no more than 16 l / s when drilling with a bit with a diameter of 530 to 217 mm, no more than 10 l / s when drilling with a bit with a diameter of 217 to 155.6 mm and no more than 7 l / s when drilling with a bit with a diameter from 155.6 to 84 mm.