Research and Application of the Position-Occupying Drilling String Techniques for Twin Holes in Monobores in Bohai Oilfield

In twin hole drilling, traditional technology only allows achieving an initial depth about 300.00-400.00 meters in twinhole due to limitations imposed by tools, processes and technologies. At the same time, there are some drawbacks, such as having two wells in one hole, making another hole when reaming and providing a large amount of cement. All these conditions may make it impossible to meet demands of some wells. To solve these problems, and with consideration to specific conditions of the A Oilfield in the Bohai Area, position-occupying drilling techniques had been introduced. With the combination of reconstruction, fine tuning and design optimization of hanger base and other auxiliary facilities, borehole trajectories in Well Hai 4 and Well Hai 22 were controlled independently. The depth of the φ339.7 mm casing in the first spud-in was deepened to 1, 000.00 m and 600.00 m. The volume of cement consumed was reduced by more than 50% when compared with wells of similar depths. Deployment of these techniques can effectively seal off shallow gas formations, minimize risks related to collision of boreholes and reduce the volume of cement consumption. In addition, these techniques might generate necessary safety redundancy for the second, third and other well intervals. TVD of the Well Hai 4 and the Well Hai 22 are 4428.00 m and 3173.00 m, respectively. In addition to achieve safe and high-efficiency implementation of relevant operations, these techniques can effectively reduce the time required and significantly enhance economic benefits of relevant operations.