Unconventional Single Slurry Solution for ERD Wells with Depleted Formations

Tailoring slurry designs using amorphous liquid silica base has been a success for Cementing Extended Reach Drilling (ERD) wells in Brunei in development fields. The use of this unconventional slurry density and design has helped to achieve the necessary top of cement and required zonal isolation for the production string of these wells. Cementing across depleted formations has been a challenge for the drilling sector within the oil industry. Isolation of production zones with competent cement slurries has become a necessity in fields, especially where a low Equivalent Circulating Density(ECD) during the cementing operation is required to achieve the desired top of cement in low fracture gradient formations. For Brunei offshore operations a novel approach has been proposed that uses an amorphous liquid silica-based slurry system to design a new 14 ppg lightweight cement slurry. The slurry properties were tailored to eliminate the need for a dual slurry system. Planning, execution, and post-operation evaluation methods have been developed for this new design. Extensive laboratory testing has been performed for the 14 ppg extended slurry which includes basic slurry testing as well as more advanced evaluations such as a full mechanical properties study and finite element analysis that was used compared to conventional slurry designs. Various optimizations were done for the slurry design to overcome mixability challenges and deployment using a conventional offshore liquid injection system or by premixing the water with liquid additives on a mixing tank or rig pits. To validate this technology, a field trial was performed at the rig site where a production liner for an extended reach well was cemented and subsequently evaluated using cement evaluation logging tools. The first Brunei offshore trial operation, executed in Q2 2020, was a 4.5-in. production liner where 16.5 m3 of a 14ppg novel slurry design was mixed, pumped and successfully placed within the annulus. Since the initial trial, a total of 8 jobs have been executed successfully in Brunei, with a few more wells identified as candidates for this solution. The paper provides laboratory testing details, hydraulic simulation validations along with job execution and post-operation cement evaluation.

Drilling Dynamics, Mechanical Specific Energy Data Help Drill Record Extended-Reach Well

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203335, “Using MSE and Downhole Drilling Dynamics in Achieving a Record Extended-Reach Well Offshore Abu Dhabi,” by Nashat Abbas and Jamal Al Nokhatha, ADNOC, and Luis Salgado, Halliburton, et al., prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually 9–12 November. The paper has not been peer reviewed. Complex extended-reach-drilling (ERD) wells often present challenges with regard to geological aspects of data requirement and transmittal, reactive geosteering response times, and accuracy of well placement. Such scenarios may require innovative approaches in Middle East carbonate reservoirs. The objective of the complete paper is to illustrate that, by assessing the details of reservoir geology and key operational markers relevant for best practices, drilling approaches can be customized for each reservoir or scenario. Reservoir Background and Geology The planned reservoir section is a single horizontal of approximately 25,000-ft lateral length at a spacing of 250 m from adjacent injectors. The well was drilled from an artificial island. Field A, a shallow-water oil field, is the second-largest offshore field and the fourth-largest field in the world. Horizontal drilling was introduced in 1989, and an extensive drilling campaign has been implemented since then using steerable drilling technologies. This study is concerned only with wells drilled to develop Reservoir B in Field A, which contributes to the main part of initial oil in place and production. The thick limestone reservoir is subdivided into six porous layers, labeled from shallow to deep as A, B, C, D, E, and F. Each porous layer is separated by thin, low-porosity stylolites. The reservoir sublayer B, consisting of approximately 18-ft-thick calcareous limestones, was selected as the target zone for the 25,420-ft horizontal section. ERD, constructed on artificial islands, began on 2014 with a measured depth (MD)/true vertical depth (TVD) ratio approaching 2.2:1 or 2.4:1. A recent ERD well, Well A, was drilled at the beginning of 2020 with a MD/TVD ratio of 5:1. This value is a clear indication of progressively increasing challenges since the start of the project. Mechanical specific energy (MSE) has long been used to evaluate and enhance the rate of penetration (ROP); however, its use as an optimization tool in ERD wells has not been equally significant. This may have been mostly because of historical use of surface-measured parameters, which do not necessarily indicate the energy required to destroy the rock, particularly in ERD wells. Using optimization tools as part of the bottomhole assembly (BHA) downhole close to the bit provides actual weight-on-bit (WOB) and torque-on-bit (TOB) applied to the drilling bit to destroy the rock and, thus, results in more-representative MSE measurements to optimize drilling parameters and ROP in ERD wells.

Application of Innovative Extended Reach Well Operation Technology in Nanhai East

Extended reach well (ERW) can be extremely drilled to distant reservoirs to reduce the infrastructure and operational footprint. Drilling ERW and extending their reach to greater depths requires both improved equivalent circulating density (ECD) and frictional resistance due to large horizontal displacement, long open hole and borehole unstability. ECD is one of the keys to safe and efficient drilling, especially in complex formations with narrow pressure profile, and wellbore frictional resistance appreciably influences drilling torque and drag, as well as casing running. This paper presents several methods, including continuous circulating valve(CCV) drilling technology, cuttings bed removal technology and chemical friction reduction technology, to promote the success of ERW drilling. The applications are realized by means of adding CCV, cuttings bed cleaner to the drill string and chemical friction reducer into the drilling fluid. Respectively the CCV drilling technology realizes the continuous circulation of drilling flooding, and cuttings bed removal technique utilize integrated design of hydraulic machinery with hydraulic parameter adjustment and flow passage design, to enhance turbulence velocity and strength of drilling fluid flow field, which both can effectively improve the efficiency of carrying bit cuttings, and reduce the fluctuation of ECD. Chemical friction reduction technology is mainly composed of chemical frictional drag reduction agent which belongs to organic anion compound products, and has excellent super anti-wear lubrication. Results show that the fluctuation of ECD in the high-risk well section with well loss was controlled within 2.5%, and narrow density window formation (0.18g/cm3) was drilled safely without any caving and leakage. The friction coefficient ranged from 0.4 to 0.25, with 40% decrease compared with previous wells in Huizhou Oilfield. And also the ROP increased by 45% due to effective transmission of WOB. The technologies shown in this paper comprise key innovative technologies in ERW operation in Nanhai East. Less time is occupied in equipment installation, as well as simple operation flow, however with improved stability and remarkable performance. It lays a foundation for further study of ultra extended reach wells with greater difficulty and challenge.