Paradigm Shift in Egypt's Western Desert: Premium Grade Steel-Body Bits Displacing Matrix Designs in Key Applications

Drilling the deep lithology column using PDC bits in the Obayied field of Egypt's Western Desert has been extremely difficult. The field's lithology column represents an amplification of all of the typical lithology characteristics in the Western Desert. The highly interbedded sandstone, siltstone, and shalealong with the variance of such interbedding across the field-has been a significant challenge for well planners and has adversely affected cost per foot. The application is characterized as predominantly abrasive and impact-intensive in the same section, hence challenging for PDC bit durability. To efficiently drill the 8½-in interval, a fundamental change in PDC bit design is required.Considering these formidable challenges, service providers had to evolve PDC bits to meet the constant demand of improving performance and reducing costs. Focus was concentrated on balancing new technology developments and the willingness to invest on field trials. To accomplish these objectives in the Obayied field, the operator and the service provider identified two main problems-developing an in-depth understanding of rock strength characteristics of each individual formation in the deep rock column and its variance across the field, and developing PDC bits that can survive such a challenging rock column with improved durability and ROP.Recently, a novel conical diamond element (CDE) with extreme impact-and abrasion-resistant characteristics has been developed. The CDE has been incorporated at bit center in a new and innovative PDC design, solving the traditional challenge of the inefficient characteristic of PDC bit central area. In addition, a field-wide rock strength study based on sonic and gamma rays logs provided the transparency required for better planning and risk management to resolve the operational inefficiencies traditionally seen in the Obayied field.The new PDC bits utilizing the CDE technology has been deployed in Obayied and has reduced consumption to just 3-4 bits per section in 2014, whereas that number was 8 -10 bits per section averaged in 2006. The new bit has also reduced the average number of days to drill the section from as low as 6 days to reach TD instead of 20 days. Performance gains were achieved both in ROP and footage totals in the most challenging formations, including Alam Al Buwaib, Upper Safa, and Lower Safa. The authors will discuss the benefits of this industry collaboration that achieved exceptional performance improvement leading to dramatic cost savings in the Obayied field.

The Challenge of the Obayied Field: Novel PDC Design Sets New Performance Benchmarks in Egypt's Difficult Deep Western Desert Lithology Column

Moneim¹,

Ahmad²,

Hanafy

et al. 2015

Innovative PDC Drill-Bit Cutter Technology Leads to Performance Improvements in Western Desert, Egypt

Ismail

Stockey

DiGiovanni

et al. 2015

The ongoing drilling campaign for an operator drilling in Egypt's Western desert area involved drilling vertical and directional wells approximately 5,000-to 5,500-m deep. The application involved drilling through very hard and abrasive sandstones, and intercalations of shale, sand, silt and dense dolomite inter-beds of about 25,000 psi unconfined compressive strength (UCS). Historically, poly crystalline diamond compact (PDC) drill-bit showed inconsistent bit performance that included premature bit failure and low rate of penetration (ROP), resulting in costly bit trips to the surface.New and improved bit technology was required to improve the penetration rate and footage to reduce bit trips to the surface and improve the overall drilling performance. An in-depth study of the formation properties, wireline logs, drilling parameters and bit dull analysis was performed. Detailed analysis identified this application can benefit from running cutters with a non-planar cutting face on a field-proven seven-blade PDC bit frame. The bit was run on a Rotary Steerable System (RSS) coupled with a positive displacement motor (PDM) on top of the BHA to further improve the drilling efficiency and overcome any challenges.Upon deployment, the 8½-in bit design with the new 16-mm cutters with non-planar cutting structure combined with optimized depth-of-cut control, stability, hydraulics efficiency and balling prevention features led to improved performance when drilling the complex, hook-shaped well profile (where torque and drag were an issue in the past). Compared to field offsets, the bit drilled very smoothly and aided the operator in placing the well in the correct direction with minimum bit-torque caused from bit and formation interaction. Offset bits fail to achieve the required directional plan in the past because of the severe nature of drilling in the area.This integrated solution resulted in a 15% improvement in the ROP as compared to the offsets and a 57% improvement in footage drilled. This performance replaced six drill bits, which were used to drill the same interval in the offset wells. The new innovative PDC cutter technology saved the operator at least USD 250,000 from the planned authority for expenditure (AFE) cost, as well as set two consecutive footage records. This paper outlines the problems in drilling this challenging area, the thought process behind using the various technologies incorporated in the PDC bit design and the keys to overall success.

Innovative PDC Bit Design Increases Drilling Efficiency in Egypt’s Notoriously Difficult Western Desert Deep Lithology Column

Farouk¹,

Elwekeel²,

Shokry³

et al. 2015

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.