SLB drilled three 8½-in ultradeep wells through a laminated reservoir in a hard and abrasive formation more efficiently while reducing NPT.

Operating conditions and conventional BHA lead to excessive NPT

PetroChina's Tarim basin development plan for the Hade field, located in the northwest Xinjiang region of China, called for producing 33 million tonUS of crude oil within a year. In pursuit of this goal, PetroChina planned to drill 8½-in ultradeep horizontal wells in sand reservoir formations at depths of more than 5,000-m TVD. Beyond drilling at great depths, the tight laminated reservoir being targeted is in a formation with hard and abrasive characteristics punctuated by hard stringers. The technical limitations of the rig and downhole equipment made steering very difficult, and drilling the hard, abrasive formation produced excessive shock and vibration affecting conventional BHA performance. These operating conditions required that three to five runs be made to reach a section's TD at ROPs that averaged 2.65 m/h.

RSS and bit combine to answer operational challenges

SLB run PowerDrive Archer™ high build rate rotary steerable system (RSS) and a 8½-in PDC bit from SLB. We drilled the three wells at an average of 4.65 m/h, which surpassed offset well average ROP by 75%, increased run length 113%, and saved 18 rig days.

To directionally drill the Hade field application more efficiently, SLB recommended an engineered drilling system that included the PowerDrive Archer high build rate RSS and a 8½-in PDC bit. The fully rotating PowerDrive Archer RSS provides the necessary control to maintain directional requirements while punching through hard stringers and is specially suited for high dogleg severity (DLS) applications.

The 8½-in PDC bit was selected after a performance analysis was conducted using the IDEAS™ integrated drillbit design platform. This included simulation drilling with several bits based on the BHA design and drilling parameters consistent with PetroChina's application.

Average ROP and run length in three wells set field record

When compared with drilling assemblies used in offset wells, the PowerDrive Archer RSS and PDC bit drilled the three horizontal wells at an average ROP of 4.65 m/h, representing a 75% increase in ROP. Average drilling run lengths were extended from 236 m in previous wells to 503 m, for an increase of 113%. Time-depth curves for the three wells drilled indicate a total of 18 rig days were saved on the three wells when compared with offset wells. During this time, PetroChina set several field records: 5.83-m/h ROP, 620-m single run, and 5,048-m TVD.