In Egypt's Western Desert, the Alam El-Buieb formation (AEB) and the Safa reservoirs have remained a challenge to drill because of their high compressive strengths and abrasive sandstone/siltstone formations. In the AEB and Safa formations, vertical sections are drilled regularly using several 8½-in roller-cone tungsten carbide insert (TCI) bits. To improve section performance and reduce overall cost per foot ($/ft), impregnated bits run on turbines and high speed motors were initially used. While these types of bottom hole assemblies (BHA) had advantages, they also came with disadvantages: The high- running costs and greater lost-in-hole (LIH) costs associated with these assemblies was a concern for most operators. Additionally, some rigs lacked the power to run them. These conditions motivated operators and bit suppliers to find alternative assemblies that can successfully drill challenging sections while reducing the $/ft by increasing the ROP and the footage each bit drills. Recent advancements in polycrystalline diamond compact (PDC) bit design have made this possible. By altering PDC-bit profile, shape, cone angles, back rake angles, cutters and conducting test runs while being guided by finite element analysis (FEA) based modeling system and CFD modeling, design teams have produced PDC bits that are best suited for the targeted application (formation and rotary BHA). In conclusion, the newly designed PDC bits have shown a significant increase in ROP and footage compared to TCI and impregnated bits. The result is a significant reduction in drilling costs running PDC on rotary assemblies.

Recent manufacturing and hardfacing advances have produced a steel-body PDC bit (SB-PDC) capable of efficiently drilling interbedded formations at significant depth. These technological advances have increased the bit's resistance to abrasion/erosion and enabled a new style steel-body PDC bit to drill formations in Egypt's western desert previously drilled by matrix PDC bits. Field tests have confirmed the steel-body PDC bit can outperform matrix PDCs in a wide-range of interbedded applications that contain a heterogeneous mixture of shale, sand/siltstone, and limestone. The approach combines optimized cutting structure design and premium PDC cutters that enable the steel-body PDC bit to drill the abrasive sand/siltstone component. The bit can also efficiently drill shale and soft limestone due to its hydraulic efficiency which was a factor limiting performance improvement in previous designs. The bit solution employs: ➣Cutting structure optimized using FEA-based modeling system➣Premium grade PDC cutters➣Next generation of abrasion/erosion resistant hardfacing material➣Hydraulically efficient bullet-shaped body type The new SB-PDC technology was deployed in a sequence of tests in different applications and fields in Egypt's western desert. The trials were run in different lithologies at different depths. Direct comparisons to relevant matrix PDC technology and other available steel-body bits clearly demonstrates the new-style steel-body PDC bit's value by setting new benchmarks and reducing cost/ft.

Efficiently drilling the deep lithology column with PDC bits in Egypt's Western Desert (WD) has been extremely challenging. The formations-Alam El Buwaib, Masajid, Zahra, and Safa-contain a volatile mixture of highly interbedded sandstone, siltstone, and shale that have damaged PDC bits, especially at depths of 12,500 ft and greater. In addition to the demanding drilling requirements, operators are pursuing multiple targets per well for better cost optimization. Finally, a tight control on target drilling days has required more efficient and consistent drilling solutions. In addition, the array of different drive types and BHAs used in the area have all suffered and exhibited the same symptoms: high stick/slip, high shock and vibration, failure of MLWD tools, RSS, or positive displacement motor (PDM), and premature tripping for bit changeout.To solve the issues, several 8½-in PDC bits were developed that feature a central conical diamond element (CDE). The bit designs feature an abbreviated cutting structure profile at the bit center that generates a rock column that stabilizes the bit. The rock column is constantly being destroyed with axial force as opposed to traditional shear, resulting in lower torque magnitude and fluctuations. The reduction in torque fluctuations increases the bit's potential to solve a combination of vibration issues. The new-style bits were scheduled to be field tested in different wells and runs in Egypt's Western Desert applications, including with classical rotary BHAs, with different RSS/PDM types in a variety of directional well profiles, at different depths, and in different fields. This robust field campaign was performed with the intent of proving and providing a consistent solution and grounds for a paradigm shift of how PDC bits need to be constructed.The results of the multifield campaign delivered low levels of torque and torque fluctuations; enhanced bit durability, frequently replacing two bits or more; low vibration levels; a significant increase in cuttings size, thereby enhancing surface formation identification; and high dogleg capability and smooth directional response. The bits also increased footage and overall ROP due to preserving the cutting structure, producing a performance step change and achieving consistent lower cost per foot across the WD field.The field test campaign results in Western Desert spans over 60 runs conducted over a 12-month period. A close monitoring of the performance improvement has been tracked where the runs are rated against offsets. The rating is in terms of overall run performance, footage improvement, ROP increase, cutting structure condition, and overall dull grade. The new bits set over 30 new benchmarks.

One of the perceived drawbacks of matrix polycrystalline diamond compact (PDC) bits compared with steel PDC bits is their restricted open-face volume and smaller blade standoff, which is primarily caused by the matrix PDC bits' brittle nature. Increased blade standoff gives steel PDC bits a more hydraulically efficient body type, which directly affects ROP. In many drilling applications, operators switch to steel PDC to take advantage of their hydraulic efficiency, and recent developments in hardfacing material has expanded the range of applications of such bits. However, there are applications that are still dominated by matrix PDC bits, and a need arose for matrix material that can allow the molding of slim, hydraulically efficient matrix bodies. A new matrix material with enhanced toughness allows for the design of a slim-body matrix construction. This innovative concept has been validated for structural integrity, which was the main perceived risk. The technology was rolled out for 8½-in and 12¼-in hole sections and deployed in a field test campaign in all of Egypt's different rock columns. The effect and value of faster ROP increases with application complexity and depth and is directly proportional to rig spread rate. Hence, realizing the application limits of slim-body matrix technology was the main intent of this study. Success was measured by observing the effect of hydraulic efficiency across different fields in terms of ROP and cost savings. Further, to isolate the effect of slim-body construction, several tests were conducted between standard matrix and slim-body matrix construction using the same cutting structure layout and PDC cutter grade. The slim-body matrix construction demonstrates significant improvement in cost per foot for applications and is directly proportional to UCS. This feature is advantageous in interbedded applications, where formations fluctuate from hard to soft and vice versa along the drilled column. This new feature has since been standardized in matrix bits and is being rolled out across various applications with the intent of tackling more expensive drilling operations to show a greater reduction in cost per foot.

The ability to construct slim body matrix bits has been proven and demonstrated to be of value when compared to conventional matrix construction and steel body PDC bits. The new matrix material with enhanced toughness has shown it can take the drilling and dynamic loads of medium depth applications with low to medium compressive strength. However the technical limits possible using slim body construction needs to be established. Recent developments in applications drilling deep sections in medium to hard formations with extended intervals has shown a need to have heavy set PDC bits to be more hydraulically efficient. The construction of heavy set matrix bit has always suffered from tight junk slot area and open face volume because of the high blade count and dense cutting structure. The challenge with the rock column of deep sections is interbedding between soft formations and hard formations creating a need for a cutting structure to be durable but in the same time not suffer from poor cleaning when formation transitions to a softer member column. The new matrix material with enhanced toughness allows for the design of a slim-body PDC matrix construction. The technology was initially rolled out for 8½ in and 12¼ in shallow hole sections and results are recorded in SPE-KSA-113. The scope of this study is testing the structural integrity of this construction together with its effectiveness by extending the concept to heavy set bits and deploying them in deep interbedded rock column applications. The main value sought is that the drilling complexity and costs increase in deep applications and targeting improvement in ROP would have a direct consequence on cost per foot. In this context even an increase of 5% in ROP can have a significant effect if the hole depth is at 15,000 ft TVD. Thus this study focuses on measuring the success rate fo slim body matrix by measuring rate of ROP improvement while ensuring the structural integrity of this technology is not a risk at such depths. The severity of the applications in which these tests were conducted were evaluated when possible with rock compressive strength analysis and measuring that against ROP. The results portion of this part of the campaign (deep applications) has shown surprising results with more success rate percentage of improving ROP vs what was recorded in shallow applications (see SPE-KSA-113). The cost per foot effect was even more significant at such depth with the incremental improvement in ROP as the slim-body matrix construction responded to the variation of formation compressive strength. The slim body matrix feature proved its advantage in interbedded applications, where formations fluctuate from hard to soft and vice versa with no compromise to structural integrity even at the deepest applications drilled in Egypt's rock column.