国民油井推出Valkyrie弃井系统

Plug and abandonment (P&A) operations lead to challenges removing and disposing of casing and tubing, which increases operational costs. Time-consuming milling may require the use of a rig, and plugging using poor annular cement might not provide an adequate barrier. Cementing solutions such as the Valkyrie abandonment system from National Oilwell Varco (NOV) improve cement coverage through axial and lateral oscillation to create a permanent, protective barrier, establishing an improved bond that is safe for the environment.

The Valkyrie abandonment system is part of a comprehensive well abandonment strategy that can help you safely and efficiently abandon a well. Using high-frequency hydraulic pulses, the tool vibrates free-hanging production tubing to consistently propagate cement around the annulus. Cement samples tested in the lab have confirmed that pumping cement through the Valkyrie abandonment system improves its rheology, and this solution has been proven to provide higher quality cement bonds, minimizing channeling and microannulus development. With the Valkyrie abandonment system, you can reduce the amount of pipe that must be retrieved from the well, create a positive environmental impact, and minimize costs without sacrificing the integrity of the abandoned well.

Deployed by wireline along with the packer as a sacrificial assembly, the system uses high-frequency hydraulic pulses to move free-hanging production tubing and consistently propagate cement around the annulus. The device oscillates the tubing to improve cement jobs, especially in areas where the tubing rests on the low side of the hole. By creating movement of tubing while pumping, the system reduces the phoneme of microannuli and helps create a more robust, permanent abandonment.

By reducing the amount of pipe that must be retrieved from the well, the system helps minimize abandonment costs without sacrificing the integrity of the abandoned well, increasing the efficiency of P&A operations.

Benefits

1.Innovative design – Based on our industry-leading Agitator? systems that have been used more than 50,000 times around the world;
2.Improved rheology – Lab-tested and proven to improve cement rheology;
3.Higher quality cement bonds – Better propagation of cement, minimizing channeling and microannulus development.

Case study

An operator performed a trial run at an evaluation center in a test borehole in Aberdeen. The rig test objective was to assess the axial and lateral tubing movement generated by pumping a fluid with similar properties to cement through the abandonment system. In the test procedure the operator configured the test well with 975 m (3,200 ft) of 95?8-in. casing and installed the 5-in. tubing to simulate production tubing similar to the well profile it intended to abandon. Using the Valkyrie abandonment system, packer assembly and BlackBox data sensors from NOV, the operator tested with varying flow rates and fluid densities between 14.5 parts per gallon (ppg) and 15.4 ppg. The operator concluded that the pressure pulses created by NOV’s abandonment system generated significant movement of the tubing. Cement displacement propagated past 610 m (2,000 ft) above the device. The lateral vibration magnitude attenuated from 305 m (1,000 ft) to 610 m, but it was sufficient to vibrate the tubing within maximum lateral restriction. The magnitude of the pressure pulses, acceleration and frequency of vibration were functions of flow rate. The frequency of the vibration had a more significant effect on the displacement than lateral acceleration.

The operator installed the device into a flow loop to facilitate cement circulation for the purpose of testing the cement quality after passing through the system. The cement testing confirmed that the abandonment system generated pulses that improved the cement properties. The operator pumped 20 bbl of 16-ppg cement through the abandonment system at a flow rate of 145 gal/min and collected five cement samples at one-minute intervals, comparing them with samples of the same cement that did not pass through the system.

An independent laboratory confirmed that rheology samples taken after the introduction of the abandonment system were improved.

To date, the system has been installed on 11 wells, with the volume of pumped cement increasing from job to job and in wells with up to a 30-degree inclination. Cement bond logs verified the results of 792 m (2,600 ft) of good cement out of 945 m (3,100 ft) pumped. The company has begun to use multiple installations of this process to leave additional sections of tubulars in the well.

Cement samples tested in the laboratory have confirmed that pumping cement through the NOV abandonment system improves rheology, allowing it to provide higher quality cement bonds and minimizing channeling and microannulus development. The technology has enabled operators to leave more than 9,144 m (30,000 ft) of production tubing permanently in the wellbore, eliminating the expense of pulling, transportation, cleaning and disposal.