Abstract
The operator has attempted to efficiently drill the 8-3/8, 5-7/8 sections using roller cone tungsten carbide inserts (TCI) and polycrystalline diamond compact (PDC). In the 8-3/8 5-7/8 sections abrasive wear caused by hard/sharp sandstone limited PDC life. Even the toughest cutter could not withstand the abrasivity. The operator required new cutter and PDC technology.
Engineers used numerical models to optimize the interface between the diamond table and substrate that determines the cutter's response to residual and service stresses. Diamond table properties were changed to increase durability and wear resistance. The result is an abrasion-resistant cutter capable of maintaining a sharp edge in hard carbonates and abrasive sands. Patented depth-of-cut control technology provided increased stability. Directionally drilling 8-3/8 section through hard/abrasive sandstone with 105pcf overbalanced mud is challenging. TCI, delivered poor ROP while sliding while wear resulted in short runs, lost cones, causing fishing/milling. PDC was tried previously in similar formations with minimal success (cutter wear). A baseline was set using three TCI with diamond enhancements which drilled 75ft in 36.5hrs, at average ROP of 2ft/hr (cost/ft $2240). Using the new cutter technology, four bits drilled 543ft in 116hrs at average ROP of 4.68 ft/hr at cost/ft $778. One bit drilled a record 279ft at 4.73ft/hr. The new PDC technology achieved 65% reduction in drilling cost, saving over $750,000 on one well by reducing drilling time and eliminating fishing operations
The 5-7/8" lateral is drilled through the abrasive Jauf reservoir. In the Hawiyah field, the new PDC technology drilled 1620ft of hard/abrasive sand using three bits. The first sidetrack, took nine roller cones and two PDCs to drill 1207ft. The cost/foot reduction was $283/ft for a total savings of $460,000 over this section. With improved cutter technology, a second well was drilled in the same field that required two PDCs to drill 2368ft at 16ft/hr. This performance set the lowest cost per foot horizontal section in this application.
In the 5-7/8" vertical application drilling the Unayzah formation in the Ghazal Field, new PDC technology drilled 517ft of hard abrasive formation using two bits, compared to the best offset for the same section using one impregnated bit and four TCI. The cost/foot reduction was $229/ft for a total savings of $118,000.
