Drilling to the targeted depth of a well can be a challenge, considering the problems that may arise in the form of wellbore instability, mud losses, and/or differential sticking. The objective was to successfully drill a first-time implementation of an Oil-Based Mud (OBM) system with 60:40 Oil-Water Ratio (OWR). The OBM system was maintained within the specified parameters in terms of mud weight, viscosity, and fluid loss. The addition of primary and secondary emulsifiers in the system enhanced electric stability (ES). Moreover, solid control equipment will be monitored continuously for immediate action if necessary. Contingency plan and a surplus of chemicals will be provided to ensure a smooth drilling and a swift movement of operations. A fluid system was designed after extensive laboratory tests to analyze the optimal approach to drill using the first-time application of 60:40 OWR mud. It reduces the use of Diesel consumption by 26% in total OBM formulation, lowers the percentage of Low Gravity Solids (LGS) compared to the 80:20 OWR mud, and decreases the impact on the environment. Furthermore, the OBM was then reused in consequent wells with the addition of emulsifiers to reduce the cost. This paper presents successful first-time applications of the 60:40 OWR fluid till the targeted lower Burgan formation, interbedded sandstone and shale formation. A complete laboratory analysis comparison between previous wells drilled and the current application indicates no difficulties were faced.
Liner lap testing operations in the gas fields have evolved to include shoe track drill out operations in the same trip. Typically, a drilling BHA is run and spaced below an inflow test packer to drill out the shoe track to 20ft above the shoe. A landing sub or no-go lands in the liner top at the predetermined bit depth to activate a test packer mechanically. This order of operation exposes the packer elements to debris circulated from drill out operations resulting in damage to the packer elements or incorrect engagement of the packer elements and casing ID. Deploying a hydraulically activated collapsible land sub in conjunction with the mechanical inflow test packer allows a change in the order of this operation. The collapsible landing sub is run in hole below the test packer and lands in the liner top to facilitate the packer activation. The liner lap test can be conducted with little or no drill-out debris in the well. Once the liner lap test is considered successful, the landing sub is hydraulically collapsed allowing entry into and below the liner top. Drilling operations can then resume without concern to packer element damage. Applications of this system include liner lap testing and any subsequent drilling operation in the same trip. This paper introduces and discusses the step change in operational liner lap testing procedures while incorporate this new approach to market technology of the collapsible landing sub. It describes the lesson learned and the limitations of the previous method of conducting this operation. It analyzes and compares actual job data and success rates between the previous methods and methods incorporating the new technology. This paper shows that using the collapsible landing sub in conjunction with the mechanical in flow test packer cost reduction and increases reliability and profitability in these operations.
It is a challenge to drill a highly deviated or horizontal hole in high permeable formations. High differential pressures may lead to several problems like tight holes, wellbore instability, differential sticking and mud loss while drilling across these permeable or fractured formations. It was always preferred to drill these wells with Oil base muds which showed some success. While operators always prefer the standard solution, which is casing isolation for problematic sections, challenges have increased due to continuously drilling in depleted reservoirs which leads to considerable nonproductive time. The other solution to overcome such problematic sections was to re-design a fluid system that would target drilling through serious of highly permeable sand and shale formations. The fluid system would primarily address shale inhibition along with effective bridging, minimizing pore pressure transmission and wellbore strengthen with increased hoop stress in the wellbore. Software modelling and permeability plugging tests were performed to evaluate the fluid behavior under downhole conditions and to predict the characteristics of induced micro fractures based on rock mechanics. Porosity, permeability and induced micro fractures were considered to optimize the bridging mechanism. It was identified that normal bridging solutions involving calcium carbonates and graphite material were not enough to address the pore pressure transmission problem. It was essential to include a micronized sealing deformable polymer along with normal bridging material was effective in plugging pore throats and minimizing fluid invasion. The deformable polymer component is able to re-shape itself to fit a broad range of pore throat sizes which was previously unattainable with conventional bridging technology which was confirmed by particle plugging tests. A one well was identified to be drilled in highly depleted reservoir at an inclination of almost 45 degrees. The section involving the highly depleted and permeable sand involved drilling highly stressed shale formations which requires high mud weight for their stability. This was the first attempt on a high-angle well with development drilling operations in Kuwait and was performed to facilitate the successful drilling of the reservoir. Drilling and logging were successfully performed along with logging and LWD runs with no recordable differential sticking or losses incidents. This paper also presents 2 successful applications in the same field with the application of proper bridging and utilization of deformable sealing polymer to address drilling problems through highly depleted and permeable formations while managing over balance of 3500 psi across them.
Deep gas wells exhibit characteristics such as high temperature and pressure that present challenges in terms of drilling and completions. To overcome these hindrances and deliver the wells in a timely manner, casing design has been optimized by utilizing the latest cutting-edge technology in the oil and gas industry. The subject area has numerous multiple reservoir pressures, which can be troublesome when drilling in one hole section. In the past, these reservoirs had to be isolated from each other by introducing casing strings, or take the risk of drilling through transient zones. The formation characteristics are troublesome as well. Starting from shale swelling to fractures. These shales are very reactive and force controlled drilling parameters while closely watching the fluid properties just to mitigate the trouble zone. Too many casing strings means an expensive well and high target well days. This is a complete review, which will discuss implementation of different technologies in a deep gas well. Advanced bridging agents drilling fluid enabled the well to avoid the operation risks of stuck pipe and optimize the rate of penetration through multiple reservoirs pressures. A 4 ½-in by 7-in completion system capable of 15K hydraulic fracturing was used. Innovative way of locating abnormal pressure formation, even though they are unpredictable. The paper describes a robust solution to well slimming, utilizing the latest technologies, drilling methods and fluid types, while following the original well plan.
Nowadays the global market demand for Heavy Oil is increasing and Kuwait Oil Company has a plan to increase the production of heavy oil, which is part of a long-term plan set out by parent group Kuwait Petroleum Corp. Drilling heavy oil wells needs a lot of efforts and expertise to be economically developed and produced. Gauged holes are the key for the production techniques used in this field, where cement channeling and perforation effectiveness are the main concern. To achieve this, a specific drilling fluid design was necessary. Laboratory tests and extensive research were initiated to customize the drilling fluid parameters and wellbore hydraulics necessary to achieve the objectives. The drilling fluid design goal was to provide enhanced inhibition for the clay and to provide good lubricity with a low friction coefficient to ensure smooth drilling and tripping operations in a gauged hole profile. This paper is describing the fluid behavior and hydraulics were designed in high profile to remain completely in laminar flow while drilling to minimize washout occurrence and maximize hole cleaning at low circulation rates (140 – 150 GPM) without the use of regular sweeps. The customized drilling parameters and practices, in addition to the knowledge gained from the laboratory testing phase, were transferred to the field. This resulted in field proven successes with more than 200 perfectly gauge holes being drilled. Case history from one well in Kuwait field is included in the paper.
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