PRODUCTION WELL KILLING METHOD (OPTIONS) Russian patent published in 2021 - IPC E21B43/12 E21B43/22 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil and gas industry, in particular to technologies for killing production wells during the repair and maintenance of a well with two or more productive formations. The method includes lowering into the well a production hanger, which consists of a pipe string and a pump located in the well above the productive formations, and pumping backing fluid into the well. According to the first option, no more than 3 days before killing the well, the formation pressure in each well formation is determined, the density of the drilling fluid is determined depending on the formation pressures of the productive layers according to the given mathematical expression. An aqueous solution of a surfactant with a density corresponding to the calculated density of the setting liquid is used as the presetting fluid. The volume of the drilling fluid for killing the well is determined. When the difference between the formation pressures is not more than 3 MPa, the injection fluid into the wellbore is injected in two cycles. In the first cycle, in the annular space of the producing well, the pumping fluid is pumped to the lower end of the pipe string, which is lowered into the well, after which technological holding is carried out for 3-4 hours. Then, a second cycle of replacing the well fluid with a backing fluid from the lower end of the pipe string to the wellhead is performed by pumping the backing fluid along the pipe string, without exceeding the pressure allowed on the production casing before the backing fluid leaves the annular space at the wellhead. If there is no excess pressure in the well, then the well fluid is replaced in the process of lifting the operating hanger with the addition of the backing fluid with a density of 1180 kg/m³ into the annular space of the well with a pumping unit. According to the second option, when the difference between the formation pressures is more than 3 MPa, to prevent the absorption of the drilling fluid by the formation with a lower formation pressure, temporarily blocking fluid is firstly pumped into the formation with the lowest formation pressure. High-viscosity inverse emulsion with a density of 1200-1300 kg/m³ with oil base is used as temporarily blocking fluid, volume of temporarily blocking fluid is determined according height of the formation with the lowest formation pressure counting on 2 m³ by 1 m of height of the formation. At first, a preliminary cycle of injection of a high-viscosity inverse emulsion with a density exceeding the calculated density of the backing fluid is carried out into the annular space of the well with an open pipe valve at the wellhead. When the high-viscosity reverse emulsion reaches the lower end of the pump suspension, the pipe valve at the wellhead is closed. Then, through the annular space of the production well, the first cycle of injection of the backing fluid is carried out to the lower end of the hanger, while the high-viscosity emulsion enters the formation with the lowest formation pressure and blocks it. After that, technological exposure is carried out for 3-4 hours. Then, a second cycle of replacing the well fluid with a backing fluid from the lower end of the pipe string to the wellhead is performed by pumping the backing fluid along the pipe string, without exceeding the pressure allowed on the production casing before the backing fluid leaves the annular space at the wellhead.

EFFECT: improving the quality of well killing, preserving the formation properties of the formation(s), the possibility of killing a well with several formations with different formation pressures.

2 cl, 5 dwg, 3 ex, 1 tbl