RU2439274C1 - Well construction method - Google Patents

Abstract

FIELD: gas and oil production. ^ SUBSTANCE: well construction involves drilling and fixation of direction, conductor and intermediate or operation column. Process water is used as drilling mud in drilling of intermediate or operation column. Rock caving zone is reamed, lower zone of non-caving rock is drilled. Drilling set is lifted from the well, drilling pipe string with open end is lowered into the well. Clay drilling mud is pumped through the well and displaced to the surface by process water, drilling pipe string is rotated, cement slurry is injected into drilling pipe string. When cement slurry enters annular space, rotation is stopped, and drilling pipe string is reciprocated to 10-14 m length. Cement slurry is pushed out to annular space by process water of the same density as in the well till drilling pipe strin and annular space have the same level. Drilling pipe string is lifted from the well, process maturing is performed till cement solidification, cement bridge is reamed by the same drilling set used earlier, and well construction is continued to the project level. ^ EFFECT: prevented cavern formation an drilling tool seizing during drilling.

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 a viscoplastic flushing fluid in the laminar flow regime in the annular channel of the wellbore (T.N. Bikchurin, I.G. Yusupov, R. S. 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", No. 4, 2001, 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 the laminar flow regime to the turbulent one 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 borehole, and therefore, penetration by a bit of the aforementioned interval without cavern formation, 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 viscoplastic 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 eliminating cavern formation and sticking of a drilling tool while drilling a well.

The problem is solved in that in a method for constructing a well, including drilling and securing a direction, a conductor and an intermediate or production string, according to the invention, technical water is used as a drilling fluid when drilling an intermediate or production string, drill a zone of shedding of rock and drill the underlying zone with crumbling rocks , they raise the drill assembly from the well and lower the drill pipe string with the open end into the well, a clay drill is pumped through the well mud, clay mud is pushed to the surface with technical water, the drill pipe string is rotated and cement mortar is pumped into the drill pipe string, when the cement slurry enters the annulus, the rotation is stopped and the drill pipe string is paced to a length of 10-14 m, technical cement grout is pushed water of the same density that is in the well, into the annulus until the same level is established in the drill pipe string and annulus, the stake is raised from the well NNU drill pipe, conduct technological exposure to cement has set, the cement bridge drilled out the same drilling assembly, which was used before, and continue the construction of the well to the design level.

SUMMARY OF THE INVENTION

The violation of the stability of clay rocks is accompanied, as is known, by complications of the wellbore, landslides 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 excavation 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 fixing the well, the density of the cement in the interval of the caverns 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 the 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 eliminating cavern formation and sticking of a drilling tool while 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.

Well construction involves drilling and securing a direction, a conductor, and an intermediate or production string. When drilling an intermediate or production string, technical water with a density of 1.00-1.08 g / cm ^{3 is} used as a drilling fluid. Drill the zone of shedding rocks and drill on the 5-20 m underlying zone with non-shedding rocks. The drill assembly is lifted from the well and the open end drill pipe string is lowered into the well. A clay drilling fluid with a density of 1.2-1.6 g / cm ^{3 is} pumped through a well, a clay drilling mud is displaced to the surface with process water. The drill pipe string is rotated at a speed of 60-100 rpm and cement mortar is simultaneously pumped into the drill pipe string. When cement slurry enters the annulus, the rotation is stopped and the drill pipe string is paced for a length of 10-14 m. The cement mortar is pushed with technical water of the same density that is in the well into the annulus until the same fluid level in the drill pipe string and annulus is established space. The drill pipe string is lifted from the well, the process is held for 4-6 hours before the cement sets, the cement bridge is drilled with the same drilling arrangement that was used earlier when drilling the shedding zone, and the construction of the well continues to the design level.

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.

Well construction includes drilling and fixing the direction, conductor and production casing. When drilling production casing as a drilling fluid use industrial water with a density of 1.3 ± 0.3 g / cm ³ . Drill the rock shedding zone in the intervals of 1530-1570 m and drill the underlying zone with non-shedding rocks at 10 m. The drill assembly is lifted from the well and the open end drill pipe string is lowered into the well. A clay drilling mud with a density of 1.25 g / cm ^{3 is} pumped through the well, clay mud is displaced to the surface with industrial water with a density of 1.03 g / cm ³ . The drill string is rotated at a speed of 60-100 rpm, and at the same time, cement slurry is pumped into the drill string. When cement slurry enters the annulus, the rotation of the drill pipe string is stopped and the drill pipe string is paced up and down to a length of 12 m. The cement mortar is pushed with 1.03 g / cm ³ technical water into the annulus until the same fluid level in the drill string pipes and annulus. The drill pipe string is lifted from the well, the process is held for 6 hours before the cement sets, the cement bridge is drilled with the same drilling arrangement that was used earlier, and the construction of the well continues to the design level of 1800 m.

As a result, it is possible to drill a well while eliminating caverning and sticking of the drilling tool during drilling.

The application of the proposed method will solve the problem of eliminating cavern formation and sticking of a drilling tool while drilling a well.

Claims (1)

A method of constructing a well, including drilling and securing a direction, a conductor and an intermediate or production string, characterized in that when drilling the intermediate or production string, technical water is used as the drilling fluid, the zone of shedding of rock is drilled and the underlying zone with non-crushing rocks is drilled, raised from the well drilling assembly and drill pipe with an open end is lowered into the well, clay mud is pumped through the well, clay is displaced the drilling fluid to the surface with technical water, rotate the drill pipe string and pump cement into the drill pipe string, stop the rotation when the cement slurry enters the annulus and drill pipes are paced a length of 10-14 m, cement grout is pushed with the same water density, which is located in the borehole, into the annulus until the same level in the drill pipe string and annulus is established, the drill pipe string is lifted from the well, wire ie technology to extract the cement has set, the cement bridge drilled out the same drilling assembly, which was used before, and continue the construction of the well to the design level.