Process Introduction

The coiled tubing could wash downward continuously from the oil pipe under pressure, and it is easy to wash the sand to the ground from the well-hole, and such operation could be done easily by connecting the jetting tools to the tool string of the coiled oil pipe at the bottom. The well washing fluid and sand washing fluid often use the sea water, diluted solution, foam, etc.

Technical Indicators

It could solve the wellbore sand problem for oil-water well, and the coiled tubing adopts direct cycle operating mode for sand washing, and the velocity of granule in annular shall at least be two times of sedimentation velocity of the granule, and the velocity of granule in horizontal well in annular shall at least be four times of sedimentation velocity of the granule.

Technical Applicability

The minimum internal diameter of the producing string: 6mm greater than the maximum diameter of the coiled tubing downhole tools.

Supporting Systems, Software and Tools

Sand washing fluid system: the sea water, diluted solution, foam, etc.

Software: Cerberus and Orion Unit.

Methods of Application

Connect to the coiled tubing equipment, make functional testing, run the coiled tubing, and verify the sand surface;

Inject the sand washing fluid according to design displacement after verifying the sand surface, wash the sand in a direct cycle for the coiled tubing, and sample at the return outlet for observation during the sand washing;

Wash the sand to the design location, and then lift the coiled tubing to the wellhead, and stop the pump.

Notes：Appoint specially-assigned personnel to observe the returned sand during the sand washing, if the returned sand becomes less or no sand returns, lift the coiled tubing immediately to prevent the sand from burying the coiled tubing.

Application

The coiled tubing sand washing service has been applied for hundreds of well-times, with much experience obtained.

Case Study

The Well PF-A1 in loose sandstone oilfield, with Y-type electric submersible pump and commingling production string, artificial bottom of the well of 1,860m, reservoir section of 1724.6～1810m, adopts high-quality completion mode of sieve tube, and halts the production because the sand buries the reservoir section during the production; therefore, the coiled tubing sand washing operation is conducted, as the annulus of this well is much too large, the upward movement speed of the annular granule is not sufficient, so the diluted solution is taken as the sand washing fluid to restore the production of this well successfully.

Process Introduction

Replace the high density fluid by pumping the nitrogen or low-density fluid into the coiled tubing, reduce the head of liquid of the wellbore, and form a certain negative pressure in the producing section so as to make the oil-gas well with the capacity of blowing. The coiled tubing gas lifting operation is a kind of mechanical recovery mode to make it restore blowing by artificial methods after the oil-gas well stops flowing.

Technical Indicators

Gas-liquid ratio: 50~100;

Nitrogen purity: ≥ 95%.

Technical Applicability

It is applicable to the operation, acidizing and fracturing, flow-back operation of the flowing oil-gas well.

Spraying and dust cleaning operations for the oil-gas well with sufficient formation energy.

Supporting Systems, Software and Tools

Software: Cerberus and Orion Unit.

Methods of Application

Connect to the coiled tubing equipment, make functional testing, run the coiled tubing, start up the nitrogen equipment, and inject the nitrogen by pumping according to design displacement;

After reaching the amount of returning fluid required by flowing or design, maintain the displacement of pumping nitrogen, lift the coiled tubing to the wellhead at a constant speed, detach the coiled tubing equipment and restore the wellhead.

Application

The coiled tubing sand washing service has been applied for hundreds of well-times, with much experience obtained.

Case Study

In terms of some offshore gas field, with the buried depth of reservoir of 4,000～4,500m, typical flowing production string, the formation pressure coefficient drops to 0.6～0.7 during the production and development, and the fluid stores up gradually in the wellbore, Well Y-Ax1, Y-Ax2 and Y-Ax3 stop flowing in succession; therefore, the coiled tubing gas lifting operation is conducted to restore the flowing of Y-Ax1, Y-Ax2 and Y-Ax3.

Process Introduction

The nitrogen air-tightness technology refers to the air-tightness test conducted on the flow process equipment and pipeline by nitrogen during the period that the rig is put into operation and under commissioning. The purpose of the test is mainly to verify the strength of the entire pipeline, and displace the flammable and explosive gas remained in the flow process pipeline so as to prevent the system from leakage during the gathering, transportation and production in the future, resulting in damages to the safety of the rig.

Technical Indicators

Test pressure/system operating pressure = 1.1;

Purity of test medium nitrogen ≥ 95%.

Technical Applicability

It is applicable to the air-tight test for flow process equipment and pipeline of the rig or during the gathering and distribution.

Supporting Systems, Software and Tools

The nitrogen gas-tightness is to inject the nitrogen into the tank or the pipeline to be tested for air-tightness test through the nitrogen gas generating technology by membrane.

Methods of Application

Connect to the nitrogen devices, and debug the device;

Connect to the rig process requiring air-tightness, and test the pressure of the pipeline;

Conduct the air-tightness test according to the design requirements.

Application

At present, the nitrogen gas-tightness technology has been applied in multiple offshore rigs, with cumulative application of more than 40 well-times, and the device for nitrogen gas generating by membrane works properly.

Case Study

An offshore rig was going to put into operation in 2014, and it demanded to have air-tightness test for the entire rig process, with the adoption of 600D device for nitrogen generating by membrane to conduct air-tightness operations, and detected the weaken points at the pipeline joints of the rig process, which laid a solid foundation for working safety after putting into operation in the future.