Keywords: radial drilling; Titanium alloy pipe; Ultra deep well; track
Background: Tahe oilfield is a typical high temperature and high-pressure ultra-deep well with a well depth of more than 6500m, a downhole temperature of more than 150 ℃, and a bottom hole pressure of more than 70MPa.
Tahe Oilfield adopts conventional sidetracking technology and high-pressure radial hydraulic drilling technology to increase production in order to continue to tap the remaining oil in the old area and revive the old wells. It is difficult to communicate in the nonprincipal stress direction reconstruction of carbonate reservoir, while the sidetracking cost is high, the cycle is long, and the vertical distance is large. High-pressure radial hydraulic drilling technology has a wide application prospect in Tahe oil. RDS company of the United States used hydraulic jet technology to drill a 50mm hole, up to 100m. Jianghan Petroleum Machinery Research Institute of PetroChina and Drilling Technology Research Institute of Sinopec Shengli Petroleum Engineering Company have also carried out relevant research and tests on high-pressure radial hydraulic drilling technology.
When the operating well depth of Tahe Oilfield exceeds 6000m, high-strength pipe string and large jet velocity are required, and the pipe string can transmit WOB.In order to meet the existing needs of radial drilling, the radial drilling technology using a workover rig and tubing is proposed, and the mechanical analysis and steering track design of its drilling process are carried out.
In order to solve the problems of low strength of pipe string and poor transfer of drilling pressure during radial drilling in deep wells of 6000m and above in Tahe Oilfield, the radial drilling process with workover rig and oil pipe and titanium alloy pipe is put forward, and the one-way bending steering track of straightening section is optimized by numerical simulation. The influence of track steering radius, outer diameter and wall thickness of titanium alloy pipe, and track and pipe-column gap on drilling capacity are studied. Secondly, Sensitivity analysis and parameter optimization of the above parameters are carried out by the orthogonal test method. The results show that the steering radius and clearance of the track are inversely proportional to steering resistance, while the outer diameter and wall thickness of the titanium alloy tube is directly proportional to them. Therefore, the recommended combination parameters of titanium tube and steering track are: the steering radius of the track is 600 mm, the steering angle is 30 degrees, the outer diameter of the titanium tube is 25 mm, the wall thickness is 2 mm, and the gap between the titanium tube and the steering track is 4 mm.
