Anti-Collision and Obstacle Bypassing Techniques in Cluster Wells Drilling in Shallow Layers of the PY30-1 Gas Field

In PY30-1 Gas Field, well trajectories at shallow depth in wells drilled on cluster well platforms were uncertain, and it was possible that the infill wells might collide with surrounding wells while drilling in the shallow formations. In order to solve these difficulties, anti-collision and obstacle bypassing techniques were developed. When the well trajectory was designed, an anti-collision calculation was performed using Landmark software. The kick-off point, azimuth, deflection rate and short bypassing section were selected after an analysis of the errors of adjacent well trajectories mapped on the basis of electronic multishot data. The adjacent well trajectories were corrected using anti-collision scanning again based on available indications. Then new bypassing trajectories were designed and developed. In practical drilling, a Gyro was used to measure well trajectories so that the uncertainty of well locations was reduced. Directional drilling was conducted with PDM (Positive Displacement Motor) with top angle of 1.83° in order to escape from the surrounding wells as soon as possible. In addition, monitoring operations were carried out on the signs of surrounding casing collision and the cement content of returns. Well A11 was taken as an example for anti-collision and obstacle bypassing operations with the goal of illustrating and analyzing the results. This well was 5.50 m away from Well A8H and 3.30 m from Well A5H when it was drilled to the depth of 541 m. Gradually, they increased their spacing. Thus it was possible to successfully implement anti-collision and obstacle avoidance techniques while drilling in shallow layers. The research results in this paper will provide the references for anti-collision and obstacle avoidance for similar high-density cluster wells in shallow formations in the PY30-1 Gas Field.