Dual lateral horizontal wells were drilled for China Changbei tight gas development in Ordos basin. The horizontal 8 ½" hole section is the most challenge part for efficient well construction due to the hardness and abrasiveness of the consolidated sandstone rocks. Optimized drilling performance requires the matching of appropriate drill bit technology to an application for the formation to be drilled, which can be an engineering challenge. Various types of drill bits, including TCI, PDC and Hybrid type bits are used in Changbei for continuous performance improvement.
The 8 ½" hole section consists of hard and abrasive sandstone, interbedded claystone, and conglomerates. Most drill bits suffered short runs due to severe wear in the outer region of the bit including Gauge and Shoulder area, even lost cones for TCI and Hybrid bits.
With collaborations from operators and bit vendors, based on dull review and data analysis, a new type of PDC bit was designed with advanced cutter technology. The new design was developed to increase ROP and run length, avoiding unnecessary trips in the challenging formations and improved the drilling efficiency.
The new designed PDC bit adopted short profile design, reversed circle cutter placement pattern, balanced the aggressiveness and durability with backup cutters and DOC control. PDC cutters was used for passive gauge protection to overcome the wear out due to formation abrasion.
The field trials were very successful. The new designed PDC bit improved 30% on ROP and 10% on footage per bit run than offset Hybrid bits. Moreover, the new designed PDC bit eliminated lost cone risks of TCI and Hybrid bits, which was happened a couple of times in Changbei and caused tremendous NPTs for fishing and sidetracks.
This article will describe the bit performance improvement journey of Changbei tight gas field. Even with a long period of time staying on plateau, step changes still possible with new technology deployment and continuous improvement mindset.