RU2171352C2 - Method of restoration of wellbore passability after wall caving - Google Patents

Abstract

FIELD: drilling of oil and gas wells, particularly, restoration of wellbore passability after wall rock caving. SUBSTANCE: method includes assembly of bottom-hole string consisting of drill bit, drill collar, drill pipes. Said assembly is run into well, given rotary motion and circulation is initiated. Lowering of bottom-hole string with circulation is carried out to zone of rock accumulation and landing on it. Then, bottom-string is separated from rock, given rotary motion and quantity of injected drilling mud is reduced. Large rock pieces are broken by drill bit from suspended position. In case of wedging, drill bit is lifted above caving zone and process of breaking is repeated. After drill bit passing through a part or through all caving zone, circulation is intensified to maximum without passes zone to wash out fine cuttings from well up to full elimination of drawing-in and wedging. EFFECT: higher efficiency of restoration of well bore passability after wall caving.

Description

 The invention relates to the drilling of oil and gas wells and, in particular, is aimed at restoring the permeability of the trunk after a rock collapse.

 A known method of cleaning the wellbore from accumulated rock, which consists in pumping packs of high viscosity and excellent density compared to the used drilling fluid [1].

 The disadvantage of this method is that it requires a selection of parameters of the pack for the conditions of the well, removing the pack from the circulation system after pumping it, and also requires replacement (BHA). All this reduces the effectiveness of restoring patency of the wellbore.

 The closest in technical essence and the achieved result is a method of cleaning the wellbore from rock [2]. The method consists in collecting the bottom of the drill string assembly consisting of a chisel (UBT), a reamer and drill pipes. The layout is lowered into the well, being worked out and the pumps are switched on for intensive flushing.

 The disadvantage of this method is that during intensive flushing, large pieces (20-50 mm or more) are carried away from the bottom and, accumulating above the bit, enter the gap between the pipes and the wall of the borehole, wedges occur, tool tightening that ends when the rock collapses sticking and breaking pipes. Each time the rinsing is turned off, the assembly is jammed by the settled rock raised by intensive rinsing above the bit. These disadvantages reduce the effectiveness of restoring the patency of the wellbore after a rock collapse.

 The aim of the present invention is to increase the efficiency of restoring the patency of the wellbore after a rock collapse.

 This goal is achieved by the fact that in the known method of restoring patency of a wellbore after a rock collapse, which includes assembling the layout of the bottom of the drill string, consisting of a drill bit, drill collar, drill pipes, lowering it into the well, reporting rotation and turning on flushing. According to the invention, the descent of the assembly with washing is carried out to the rock accumulation and planting zone, then it is torn off from artificial slaughter, rotation is reported, the amount of washing liquid injected is reduced, and large pieces of rock are destroyed by the bit from the “overhang”, when the spalls occur, the bit is raised above the collapse zone and repeated the destruction process, after passing through the bit or part of the entire collapse zone, without stopping rotation, include flushing to the maximum possible value and, pacing the layout within the passed zone, washed (chipped) drill cuttings from the well.

 The essence of the method.

 Assemble the layout of the bottom of the drill string: chisel, (UBT), drill pipe. Then the assembled assembly is lowered into the well. In this arrangement, rotation is reported and flushing is turned on. The descent of the assembled assembly with rotation and washing is carried out to the zone of rock accumulation and getting a landing on it. If a landing is obtained, the layout is torn off from the accumulated rock until the cessation of cessation. Raise the layout above the rock collapse and with maximum washing clean the wellbore. After that, the assembly is lowered to the collapse zone and large pieces of rock are destroyed with a chisel with maximum washing. When spells occur, the bit with the layout is raised above the rock collapse zone and the destruction process is repeated.

 After driving part or all of the zone of rock collapse, without stopping the rotation, include flushing to the maximum possible value and, pacing the layout within the passed zone of the collapse, wash out the (fine) cuttings destroyed by the bit from the well.

 The operation of cleaning (destroying accumulated pieces of rock) of the wellbore from the collapsed rock is repeated until the entire wellbore is cleared of the rock and the puffs and spells are removed. Having reached the bottom, an intensive flushing of the well and processing of the drilling fluid are carried out - its parameters are adjusted to the requirements of the design and technical specifications.

 With further deepening of the well at the first signs of rock collapse (appearance of spells), the normal deepening process is terminated and the well is cleaned of collapsed rock in the manner described above.

 Example. In the well after the collapse of the rock, which was determined by the jamming of the bit and the analysis of the drilling process of neighboring wells, the cross-country ability of the well was restored.

 The assembly, assembled from a bit ⌀ 215.9 mm, drill collars and drill pipes, was lowered into the well to the zone of rock collapse and obtaining a landing. During the descent, the rotation was reported to be V = 6O rpm and flushing was turned on (flow rate 25 l / s).

 After receiving the landing of the layout, it was raised above the rock collapse zone by 0.5 m (there was no tightening), the amount of flushing fluid injected was reduced to 8 l / s and lowered, while large pieces of rock were destroyed with a chisel from the canopy and with intensive flushing (25-28 l / sec) spent cleaning the wellbore from fine sludge.

 When spells occurred, the layout was again raised over the artificial face and lowered. The process was repeated until the termination of the chisels of the bit and the normal passage of the layout along the trunk.

 After passing through the zone of rock collapse with a chisel, the layout was lifted and, without stopping rotation, the amount of flushing fluid was increased to the maximum value (25-28 l / s) and the wellbore was cleaned of accumulated sludge.

 Within the whole or part of the collapse zone, the layout is paced and the fine cuttings destroyed by the bit are washed out of the well.

 The present invention will improve the efficiency of work and ensure the restoration of patency of the wellbore after a rock collapse, to eliminate breakage of the drill string when spliced in large pieces of rock.

Sources of information
1. Rasizade Ya.M., Kurdachev A.I. Letitsky A.V., Sherstnev N.M. Experience in using a viscoelastic separator to clean a wellbore while drilling and attaching it. RNTS, ser. "Drilling". - M.: VNIIOENG, N 12, 1975, p. 35, second column, 3rd paragraph.

 2. Rasizade Y. M., Kurdachev A. I., Letitsky A. V., Sherstnev N. M. Experience in using a viscoelastic separator to clean a wellbore while drilling and attaching it. RNTS, ser. "Drilling". - M.: VNIIOENG, N 12, 1975, p. 33, the first paragraph - adopted as a prototype.

Claims (1)

 A method for restoring patency of a wellbore after a rock collapse, including assembling a layout of the bottom of the drill string consisting of a drill bit, drill collar, drill pipes, lowering it into the well, sending a message and flushing activation, characterized in that the lowering of the layout with flushing leads to the rock accumulation zone and getting a landing, then tear off the bit from the accumulated rock, report the rotation and reduce the amount of pumped wash liquid, with a chisel from the "overhang" they destroy large pieces of rock, when chipping occurs, the chisel pr raise above the collapse zone and repeat the destruction process, after the bit or part of the entire collapse zone passes, without stopping rotation, turn on washing to the maximum possible value and, pacing the layout within the passed zone, wash the fine cuttings destroyed by the bit from the well at maximum washing, the process is conducted to normal without puffs, landings passing on the layout table.