New HTHP Cutter Technology Coupled with FEA-Based Bit Selection System Improves ROP by 60% in Abrasive Zubair Formation

Abstract

Efficiently drilling the abrasive Zubair sandstone is one of the Middle East's most daunting challenges. Adding to application complexity, the pyritic formation is also interbedded with hard shale streaks and has a compressive strength that ranges between 3-10kpsi. In Kuwait, the formation is first encountered at a depth of approximately 9000ft and been drilled with mixed performance results based on bit diameter. Generally, the large diameter PDC bits are still struggling to achieve the durability objective with some wells requiring more than two PDCs to complete the short 1400ft hole section. In the smaller hole sections, technological advances have overcome the cutter/bit durability issue but with no significant improvement in ROP. The objective of an intensive bit optimization effort has focused on increasing penetration rates while striving to improve overall bit life/cutter durability. To accomplish the operator driven objectives without time-consuming field trails, the drilling team used a software system to calibrate rock strength. This data was used in conjunction with an advanced FEA-based modeling system to analyze different PDC cutting structures to select a PDC bit with the blade count and shearing configuration that would produce dynamically stable drilling. The bit body would be equipped with a new O2 cutter to increase abrasion resistance and maintain temperature at the cutter tip by using: 1) enhanced HTHP sintering process; 2) refined post-pressing process to improve thermal stability 3) optimized hydraulics to maximizing cutter cooling.

Multiple-Point Geostatistical Lithofacies Simulation of Fluvial Sand-Rich De-Positional Environment: A Case Study from Zubair Formation/South Rumaila Oil Field

“…It is located between two dolomite limestone and shale formations that are named Shuaiba and Ratawi, respectively. Zubair formation encompasses mainly sandstone with some inter-bedded shale zones as mentioned before (Al-Muhailan et al, 2013). Figure 3 shows the stratigraphic column with vertical lithology description and well log indications for all zones in South Rumaila oilf ield.…”

“…The overall Zubair formation was deposited through deltaic, estuarine and fluvial environments (Harris et al, 2012). The upper shale member, which is located above upper sandstone member, was deposited in a wave/shoreface and offshore-dominated environment resulting in sand channels that extend East-West across the anticline (Al-Muhailan et al, 2013). The upper and middle sandstone members were deposited in a tidal/estuarine environment in which the sand channels are stacked and prevailed everywhere across the formation.…”