Leak stopping high-density bound water well killing fluid

Abstract

The invention relates to a leak stopping high-density bound water well killing fluid. The leak stopping high-density bound water well killing fluid is prepared through the following steps: adding NaCl, potassium formate, CaBr2 or ZnCl2 into water to make the density of weighted water reach 1.1-2.0g / cm<3>, adding 2wt% of a nonionic surfactant polyoxyethylene ether compound osmotic agent (JFC), 0.5wt% of an imidazoline corrosion inhibitor, 2wt% of potassium chloride, 0.003-0.005wt% of phosphono-based maleic acid-acrylic acid copolymer, 0.1-0.8wt% of sodium sulfite and 2.5-4wt% of an FM super gel particle into the weighted water, and adding 1t of a high water absorption resin polymer into each 20-25m<3> of the above obtained liquid. The well killing fluid can bind different densities of brine with the weight above 12-20 times the weight of the well killing fluid, and allows the content of free water to be smaller than 10%; the surface tension of the well killing fluid is smaller than 35mN / m; when the crack width is 1-8mm, the plugging rate is greater than 99%, and the bearing strength is not lower than 7Mpa; and the 30min water loss determined by using a drilling fluid filtration instrument under 0.7MPa at 85DEG C is smaller than 10% of the whole well killing fluid, and the stabilization time at a high temperature of 120DEG C can reach above 360h.

Description

technical field [0001] The invention relates to a method suitable for medium and high pressure oil and gas well kill (workover) operations to protect reservoirs with a density of 1.1g / cm 3 -2.0g / cm 3 The high-density irreducible water workover and killing fluid of the well-entry fluid plugging type. Background technique [0002] The workover fluids used by domestic oil and gas fields for high-pressure gas well operations are mainly polymer solid-phase brine kill and workover fluids, solid-free brine kill and workover fluids, and mud-improved kill and workover fluids. Among them, the polymer solid-phase brine well kill and workover fluid has the advantages of less fluid loss and good sand-carrying performance, but for low-porosity and low-permeability formations, the solid phase damage is large, the water lock damage is serious, and it is not easy to flow back; while the mud-improved type Killing and workover fluids have relatively large damage to formations because of thei...

AI Technical Summary

Problems solved by technology

Among them, the polymer solid-phase brine well kill and workover fluid has the advantages of less fluid loss and good sand-carrying performance, but for low-porosity and low-permeability formations, the solid phase damage is large, the water lock damage is serious, and it is not easy to flow back; while the mud-improved type Killing and workover fluids have relatively large damage to the formation because of their high solid content

Therefore, many oil fields have selected and used solid-free brine well kill and workover fluid. The biggest feature of this kill fluid is that it is easy to flow back, but at the same time, it has the problem of large filtration loss, which seriously damages the formation.

[0003] Most of the current killing fluid systems do not have the plugging performance for the lost formation, and the serious leakage in the fractured reservoir during the workover process makes the pressure drop of the workover fluid column due to the loss in the workover process, not only can not be well Well kill, blowout may even occur in the workover process, leading to accidents

At the same time, the leakage has caused great damage to the reservoir. After the workover of many wells, the production has been greatly reduced, and it is difficult to restore to the original level.