SU1675545A1 - Method for bottomhole acid treatment - Google Patents

Abstract

The invention relates to the oil industry, in particular to methods of acid treatment of the well bottom zone. The goal is to increase the efficiency of the method due to the removal of calcium and magnesium sulfate from the bottom-hole zone of the sediment. The injectivity of the bottom-hole zone, the pressure and the rate of injection of the solution are determined. A 15% waste sulfuric acid is pumped into the bottomhole zone and forced into the reservoir with water. The well is held for 8–12 hours, after which it is allowed to work with depression, 0.1–0.2 MPa more than the technological mode provides, until production in the amount of 10–15 volumes of the first space of the processed part of the well bottom zone is received. Then the well is transferred to the normal process mode. The increase in oil production is 0.6-0.7 t / day per 1 well. 3 tab.

Description

The invention relates to the oil industry, in particular to methods of acid treatment of the well bottom zone.

The aim of the invention is to increase the efficiency of wellbore zone treatment with sulfuric acid solutions due to the removal of calcium and magnesium sulfate deposits from the wellbore zone.

The method is carried out as follows.

After stopping the well, inspect the bottom. If the filter is closed, the sand plug is rinsed and downhole pressure and temperature are measured. The pump tubing is lowered into the well 1–3 m above the upper perforation holes. At the well head, standard drilling equipment is installed, water is pumped in, and the bottomhole response rate is determined. Based on the results of determining the injectivity of the treated formation and taking into account the state of the production string, the permissible pressure and rate of injection of the solution are determined. From a tanker truck with a flexible hose, a solution of 15% spent sulfuric acid (USC) is fed into the reception of the filling unit and pumped through the tubing into the bottomhole formation zone.

Then proceed to the injection of the estimated amount of pressure water. After completing the download in order to prevent

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sedimentation and cementing of sediments formed in the pores as a result of the interaction of acid with carbonates, the well is put into operation after holding for 8 to 12 hours. The flow is called when the pressure differential increases from 0.1 to 0.2 MPa compared to the process by increasing the immersion of the submersible pump or the length of the swing of the pumping machine, or by increasing the number of its swings, changing the volume of the working agent, etc. In the initial period, to ensure the normal operation of the submersible pump, it is possible to pour fluid into the well to reduce the concentration of sediment withdrawn from the bottomhole zone. After receiving from the well production in the amount of 10-15 volumes of the pore space of the treated part of the well bottom zone, the latter is transferred to the usual process mode.

The method is tested under laboratory conditions on a model of porous sulfur filled with natural productive sediment rock, whose properties are listed in Table 1.

The model of the porous medium is carefully vacuumed and saturated with fresh water, after which water permeability is determined. Then the water is replaced with a solution of 15% waste sulfuric acid. In experiments on changes in hydrocarbon permeability, a porous medium is saturated with kerosene and permeability is determined. Then kerosene is replaced by oil. After 24 hours, one pore volume of a 15% solution of USC is pumped into a porous medium saturated with oil and the hydrocarbon permeability of the porous medium is determined by filtration of kerosene under various conditions.

In the first stage of the experiments according to the prototype, the system was left at rest for 24 hours to proceed to the reaction of CSCs with carbonates of the porous medium, and then the permeability of the porous medium to water was again determined with a depression equal to 0.05 MPa. The determination of water permeability is carried out repeatedly after filtering every 3 pore volumes of pores up to 24 pore volumes inclusive.

In subsequent experiments (2-10), both the CSC holding time in a model of a porous medium and depression during water filtration are changed. The permeability of the porous medium is also evaluated after filtering every 3 pore volumes of water up to 24 hours of volume, inclusive.

In a similar way, permeability measurements of a porous medium for hydrocarbons are carried out.

The results of the experiments are given in table. 2 and 3.

As can be seen from the data table. 2, when processing the porous medium of the prototype (experiment 1}

the initial permeability of the porous medium is not restored even after filtration of 24 pore volumes of water. Apparently, the prolonged exposure of the CSC solution for 24 h leads to the formation of

There is more precipitation of calcium and magnesium sulphate, which, precipitating and cementing in the pores with a depression of 0.05 MPa, is not carried away by water from the terrigenous rock. With a decrease in the duration of CSC in a porous medium and an increase in depression, the efficiency of increasing the permeability of a porous medium increases (experiments 2–10). The best results are achieved when the CSC solution is aged.

0 in a porous medium for 8 hours and the subsequent filtration of water with a depression of 0.1 - 02 MPa above the depression according to the technological mode of operation.

In this case, the permeability of porous

5 in comparison with the initial water environment increases by 5–24% and after filtering 15–18 pore volumes it does not increase, and therefore further water filtration is impractical. Under field conditions, this usually corresponds to the operation of a well at an elevated depression for 2–3 days.

As follows from the data table. 3, the optimal reaction time of the CCA from the pore to the filtration of hydrocarbons is also 8 to 12 hours.

Examples of the method on two wells

1. Forbidden hole 850 m, filter 786 - 0 796 m, reservoir pressure and temperature

respectively 1.95 MPa and 37 ° C. The density of oil and water, respectively, 933 and 1020 kg / m3.

Reservoir water is hydrocarbonate-sodium of the type. The well was operated by a deep well pumping method with a daily flow rate of 1.4 tons of oil.

2, Bottom hole 532 m, filter 495-532 m, reservoir pressure and temperature

0 respectively 2,215 MPa and 28 ° C. The density of oil and water, respectively, 1) 30 and 1019 kg / m-5.

Reservoir water is hydrocarbonate-sodium type.

5 The wells are operated using the downhole pumping method with a daily flow rate of 0.3 tons of oil and 0.2 m of water.

For treatment, 7.0 m3 of a 15% aqueous solution of spent sulfuric acid is pumped into each well.

the process of sulfuric acid purification of petroleum oils and petroleum products.

After treatment, the wells are stopped for 8 hours to complete the reaction of the interaction of the acid with the formation carbonates, and then, with an increase of 0.1 MPa, they are put into operation.

After 3 days, the wells are switched to normal operation.

As a result of applying the proposed method, the oil production rate increased, respectively, by 0.6 and 0.7 tons / day.

Claims (1)

Invention Formula The method of acid treatment of the wellbore zone, including injection into 0 The bottomhole zone of the spent sulfuric acid solution, characterized in that, in order to increase the efficiency of the process by removing calcium and magnesium sulfate from the bottomhole zone, the spent sulfuric acid solution is kept in the bottomhole zone for 8 to 12 hours, after which the depression is pumped to 0.1–0.2 MPa more than depressed during operation, until production in the amount of 10–15 volumes of the first space of the treated part of the bottomhole zone of the well, and then create a depression equal to depression during operation. Table 1 table 2