Methods to find channels for oil and water wells in underground operations

The process of determining the position of the channel section between oil and water wells is called channeling. When oil and water wells have channel channeling outside the customs clearance, they should be sealed in a timely manner. Before sealing the channel, the first issue is to accurately find the location of the channel so that targeted measures can be taken to restore normal production of the oil and water wells. Commonly used channeling methods include well logging test channeling and mechanical packer channeling.

Well logging tests include acoustic amplitude logging, isotope tracer logging, well temperature logging, well temperature and continuous flow caliper logging, and neutron lifetime Logging to find channels and MFE instrument testing to find channels using negative pressure method, etc.

1. Sound amplitude logging to find channeling

(1) Lift the original well pipe string and lead the well to the artificial well bottom or 30m below the predicted well section;

(2) Clean the well with workover fluid twice the wellbore volume and pull out the pipe string;

(3) Sound amplitude logging;

(4) Determine the channel channel location.

2. Isotope tracer logging to find channels

(1) Wellbore preparation: carry out sand flushing and well dredging;

(2) Well cleaning and testing squeeze;

(3) Measure the radiation baseline I;

(4) Run the pipe to 30m above the pre-channeling well section;

(5) Improve the wellhead, Test the pressure of the wellhead and pipeline, and the pressure shall not be lower than 1.2 times of the squeeze pressure;

(6) Use workover fluid to push the isotope tracer fluid from the tubing to 10m below the pre-channeling well section, and close the Well diffusion pressure;

(7) Clean the well and wash out the isotope tracer liquid in the wellbore;

(8) Measure the radiation curve II, compare it with the baseline I, and determine the location of water channeling .

3. MFE instrument testing negative pressure method to find channel

(1) Principle of negative pressure method to find channel

Negative pressure method to find channel is to use U-shaped tube The working principle of , the liquid in the annulus enters the channel outside the casing and the cement sheath through the holes in the upper engineering section, flows to the holes in the lower perforation section, and finally enters the test tool to obtain the channeling flux and pressure data; and then through comprehensive analysis and comparison To determine whether channeling occurs outside the casing. The on-site construction method is to lower the MFE test instrument to the channeling layer, seal the packer seat, open the test valve after a delay, and observe whether the liquid level in the casing annulus drops. If the annulus liquid level drops, kill fluid of the same performance is quickly replenished on the surface, the well is shut in for pressure measurement, and the fluid is filled to the wellhead. Unpack the packer and pull out the test tool for pressure card interpretation.

Taking the MFE test instrument as an example, the test string structure from bottom to top is: external pressure gauge + grooved liner + Y221 (P-T) packer + safety joint + jar + inner Pressure gauge + locking joint + MFE test instrument + drill collar + circulation joint + drill pipe to the wellhead.

(2) Technical key points of negative pressure method for channeling operation

(1) Hole repair: supplementary shot engineering section, shot thickness is 0.5-1.0m, hole density is 16 holes/ m;

(2) Open the well and scrape the wall. Select the well-passing gauge and casing scraper that meet the requirements; pass the well and scrape the wall to 50m below the bottom of the perforation section in the lower part of the channel; then reverse-circulate the well for 1.5-2.0 weeks;

(3) Under the MFE testing instrument, the Y221 (P-T) packer depth is 15-20m above the top boundary of the upper engineering section. The height of the liquid cushion added must meet the design requirements, and the annulus liquid level must be at the wellhead (P-T: packer available for testing).

(4) Pressurize and seal, open the well, and observe whether there is any change in the casing annulus liquid level. If the annulus liquid level does not drop, it means that the P-T packer and test string are sealed; otherwise, they should be Lift out the inspection and reinstall the channeling string.

(5) Unblock and adjust the pipe string so that the depth of the Y221 (P-T) packer is between the channeling layers, but should avoid the position of the casing coupling.

(6) Pressurize the seat and seal again, open the well, and observe whether the liquid level in the annulus has changed. If the liquid level drops, it is required to accurately measure the amount of liquid poured into the casing annulus; close the well and measure the pressure .

Generally, it is appropriate to use one opening and one closing. The time of opening and closing the well should be determined according to the specific conditions on site; after one opening and one closing, it will move to the next process.

(7) Unblock the packer. Lift the Y221 (P-T) packer to 15-20m above the top of the upper engineering section. Before sealing, the annulus must be filled with liquid to the wellhead. Then seal again, open the well, and observe whether there is any change in the liquid level in the casing annulus. If the liquid level does not drop, it means that the Y221 (P-T) packer and test string are well sealed, otherwise the channeling must be re-inspected.

(8) Take out the test tool and explain the stress card.

(9) Comprehensive analysis of the test pressure card interpretation results, on-site fluid filling volume (channeling flux) data, and sound amplitude logging data, etc., and finally confirm whether there is channeling outside the casing.

4. K344 packer channeling

(1) Preparation work

(1) The thickness of the interlayer for channeling should comply with: well depth <1500m , the interlayer thickness is >1.0m; if the well depth is between 1500-2500, the interlayer thickness is >3.0m; if the well depth is >2500m, the interlayer thickness is >5.0m.

(2) There are no falling objects in the well and the casing is intact.

(3) The basic information of the channeling well is complete, the cementing quality and the depth of the upper and lower casing couplings of the channeling well section are clear.

(4) When the channeling well section does not have access holes, additional observation holes should be shot in the interlayer of the suspected well section. Shoot 4-5 holes every 0.5m, and the holes should be evenly distributed.

(5) Arrange the pipe string according to the sequence of pipe string connection:

a. Single K344 packer: from bottom to top are the ball seat, choke, packer and upper part Oil pipe.

b. Double K344 packers: from bottom to top are the bottom ball seat, packer, oil pipe, choke, packer, and oil pipe, as shown in Figure 4-1.

Figure 4-1 Schematic diagram of double K344 packer channeling

1-oil layer; 2-throttle; 3-packer; 4-check valve; 5- Artificial well bottom

(6) Equipped with cement trucks and workover fluid that meet construction requirements.

(2) Operation steps

1. Kill the well

(1) Select a kill hydraulic well with appropriate density according to the design requirements.

(2) During the well killing process, pay attention to the changes in wellhead pump pressure, inlet and outlet displacement, and relative density of the killing fluid, so that the well killing will not cause overflow or blowout, nor will it cause leakage, Press down the oil layer.

2. Lifting the pipe string

(1) Remove the wellhead and install the wellhead BOP that matches the wellhead pressure level;

(2) Test Use the oil pipe hanger to carry out normal pipe string lifting operations after the hook load is normal.

3. Sand exploration surface and sand flushing

Lower the sand flushing pipe string (with a sand flushing pen tip at the bottom) to explore the sand surface. If there is sand, flush the sand to the bottom of the artificial well.

4. Well opening

(1) The outer diameter of the well opening gauge should be 6-8mm smaller than the inner diameter of the casing, and the length should be greater than 1200mm.

(2) Use the well guide to guide the well to 50m below the channeled layer, and less than 50m to the artificial well bottom. Observe the weight gauge reading at any time. If there is any obstruction during the well opening process, the pressure should not exceed 30KN, and sudden hard pressure is strictly prohibited.

5. Scraping

(1) The casing scraper scrapes to 50m below the channeling layer, and scrapes less than 50m to the artificial well bottom.

(2) The scraping technical requirements refer to the casing scraping operation requirements (Principles and usage of casing scrapers for downhole operations)

6. Finding channels

(1) Place an order for a packer, move the pipe string to the sealing position required by the design, and install it at the wellhead.

(2) The single packer channeling string structure (from top to bottom) is: tubing + K344 packer + choke + ball seat.

(3) Connect the inlet and outlet pipelines of the cement truck. The pressure test value of the ground pipeline is 1.2-1.5 times the working pressure. If there is no leakage for 5 minutes, it is qualified.

(4) Clean the well in a circulating cycle and wait for clean water to return from the outlet before pitching.

(5) For sealing inspection, the positive holding pressure is 10MPa for 10-30 minutes. If there is no return volume (overflow volume) or no change in casing pressure, it is qualified.

(6) Adjust the pipe string to the channeling position.

(7) Inject positive pressure at three pressure points of 8MPa, 10MPa, and 8MPa for 10-30 minutes respectively, and observe and record the changes in casing pressure or overflow volume. If the change in casing pressure is greater than 0.5MPa or the difference in overflow volume is greater than 10L/min, channel channeling is initially considered.

(8) Relieve pressure, lift the packer above the perforation section and seal it, verify the sealing performance of the packer, thereby ensuring the reliability of the channeling data.

(9) Backwash the well with clean water for 2 weeks, wash out the balls, lift out the channeling pipe string, and complete the channeling construction.

(3) Technical requirements

(1) When finding channels for new wells, casing scraping should be performed first.

(2) The workover fluid is required to be free of impurities and the pipelines and metering pools are clean.

(3) There is serious sand production in the formation. When lifting the packer after measuring a point, the pressure should be released actively and the packer should be lifted slowly. The speed should be less than 10m/min to prevent drilling accidents caused by sand production in the formation. .

(4) If the pipe string is measured accurately, the packer should be seated in the interlayer of the section to be logged and should avoid the casing coupling.

(5) When looking for channels, activated water or crude oil should be used in the oil layer to prevent contamination of the oil layer. Do not inject workover fluid or dirt into the formation channel.

(6) Data collection:

a. Well opening (scraping) and sand flushing data;

b. Observation of perforation well sections and perforating guns Type and number of holes;

c. Channeling date, channeling layer, well section;

d. Pipe string structure and schematic diagram;

e. Find the name, performance, injection (extrusion) pump pressure, observation time, injection volume, return volume (channeling flux), oil pressure and casing pressure change values ??of the workover fluid used for channeling;

f. Leak test status of oil pipes and packers;

g. Conclusion.