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During drilling operations, a pipe is considered stuck if it cannot be freed from the hole without damaging the pipe, and without exceeding the drilling rig's maximum allowed hook load. Pipe sticking can be classified under two categories: differential pressure pipe sticking and mechanical pipe sticking. Complications related to stuck pipe can account for nearly half of total well cost, making stuck pipe one of the most expensive problems that can occur during a drilling operation. Stuck pipe often is associated with well-control and lost-circulation events--the two other costly disruptions to drilling operations--and is a significant risk in high-angle and horizontal wells. Drilling through depleted zones, where the pressure in the annulus exceeds that in the formation, might cause the drillstring to be pulled against the wall and embedded in the filter cake deposited there (Figure 1).
Extended reach horizontal wells face significant challenges in drilling longer laterals with oil-base mud (OBM). A novel solid-state lubricant was developed to close the gap in limitations of liquid lubricants and OBM with respect to lubricity in long extended lateral sections. The novel solid lubricant reduces the surface contact area between the asperities (deformations) by rolling and provides a chemically bonded film on the contact areas to reduce the amount of shear stress between the surfaces.
There is limited understanding of the complex mechanisms affecting the coefficient of friction (COF). The principles of Tribology (the science of friction, lubrication and wear) were used to develop the solid-state lubricant. The Stribeck Curve describes the regimes while using a lubricant, including boundaries mixing elasto-hydrodynamic and hydrodynamic lubrication. Liquid lubricants are limited at controlling boundary conditions where the COF is ruled by asperities in contact between the surfaces. The novel solid-state lubricant works on the asperities of both the wellbore and bit/BHA. In addition, the COF is improved in the mixed and elasto-hydrodynamic lubrication regimes.
Several oil-based mud field samples were tested for lubricity using different methods including the EP Lubricity Meter and Dynamic Lubricity Evaluation Monitor (LEM). The novel solid-state lubricant was also tested using a Tribometer to produce a continuous Stribeck curve that enables evaluation of the lubricant in the entire lubricity regime. The results of the COF using EP Lubricity Meter were transformed calculating the Stribeck number to build the curve. The potential benefits of the solid lubricant were discussed using a model developed by the Stick Slip vibrations with Stribeck curves. A reduction of COF in the boundary lubrication region occurs when the asperities of the wellbore and the bit/BHA are in contact. This is explained by the adsorption and absorption of the novel solid-state lubricant onto the asperities, providing a smooth surface. The novel solid-state lubricant has a wide particle distribution (PSD) to cover different size and height of asperities. The Stribeck curves of the novel solid-state lubricant show that the lubricant can reduce COF in the boundary lubrication region where friction forces are highest, compared with a base fluid and other liquid lubricants.
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The requirement for intervention operations in extended-reach wells continues to grow. It is estimated that globally around 30-40% of the end sections of the extended-reach wells are inaccessible by the current coiled tubing (CT) friction reduction technologies, such as lubricants, vibratory tools, and tractors. Although many of the extended-reach wells are open-hole, there is a lack of understanding in the industry regarding the predictable and consistent friction reduction performance at downhole conditions of the existing CT technologies in those open-hole wells.
Conventional friction reduction techniques for CT operations have been focused around mechanical or chemical methods for cased wells. For instance, following an extensive laboratory testing research program, a lubricant was recently developed that lowers the CT coefficient of friction between 40 and 60% in new, clean wells (
The instrument previously used for metal-on-metal friction reduction research was modified to mimic the downhole conditions of CT sliding movement in open-hole wells and cased-hole wells with sand or proppant. That is, the coefficients of friction between the CT metal surface and the non-metal surface of a rock and sand or proppant layer can be measured. This instrument was designed for researching the effects of temperature, pressure, CT sliding speed, surface roughness, and fluid composition on the coefficient of friction. For clean cased-hole wells, the effects of pressure and sliding speed were weak in the laboratory tests, while the effects of temperature, surface roughness, and fluid type and composition were strong. For the friction reduction in open-hole wells, several rock samples taken from formations and reservoirs with different properties, such as porosity, permeability, pore size, etc., were used. The tests were performed with several CT coupons of different grades and both proprietary and third-party lubricants, to better understand the factors affecting the lubricity in open-hole wells. It was found that, at downhole conditions, the friction performance of the lubricant previously developed decreases from 40-60% for cased wells to 30-40% for open-hole wells.
This is the first study available in literature consisting of laboratory friction tests performed with lubricants to mimic the CT operations in open-hole wells and sand/proppant-filled cased-hole wells. Detailing the testing procedures and results are of significant help to the industry for understanding the downhole factors affecting the CT friction in extended-reach open-hole wells and for obtaining predictable and consistent friction reduction results for CT operations in those wells.
The bearing, seal, and lubrication systems of a roller cone bit are important aspects of bit life and efficiency. Roller cone bearing systems are designed to be in satisfactory operating condition when the cutting structure of the bit is worn out. To achieve this standard of bearing performance, modern goals for seal and bearing system life are 1 million or more revolutions of a bit without failure, as opposed to 300,000 or fewer in the recent past. To achieve this goal, research into bearing, seal, and lubricant designs and into materials that improve seal and bearing life is ongoing. Roller-cone bits primarily use two types of bearings: roller bearings and journal bearings, sometimes called friction bearings.
Water injection wells were planned to provide pressure support to oil producers in two North Sea fields (Field A and Field B). For both fields, water-based drilling fluid was selected to drill the reservoir section. The average permeability of the first field is 1000 mD and the second field is 50-100 mD. A laboratory study was commissioned to evaluate and optimize filter cake breaker systems for use in water injectors to efficiently remove external and internal filter cake in order to attain matrix injection without the need for backflow to clean up the sand face.
A time-delayed filter cake breaker system was chosen for evaluation as part of the study. Laboratory-scale formation damage tests indicated significant loss of injectivity, potentially due to deep invasion of xanthan polymers in core plugs along with incomplete dissolution of calcium carbonate from the filter cake. An enzyme package designed to degrade xanthan was included in the revised breaker solution and an improvement in injectivity was recorded. Further adjustments were made to the breaker formulation to optimize performance for density range, corrosion mitigation and dissolution of calcium carbonate, including allowance for the impact of the addition of lubricant to the drilling fluid.
Following an extensive and detailed study, a much greater understanding of the design, evaluation and field engineering aspects of chemical breakers has been gained. The recommendations from the study have recently been applied to injection wells on both fields.
This paper describes the test procedures adopted for evaluating the various filter cake breaker formulations and the work conducted to develop the systems to be ready for field use. The challenge and consequences around scaling up laboratory results to field conditions is particularly acknowledged. Field results are presented, highlighting both the importance of critical design issues and applied learnings for a successful outcome.
The increasing use of ecofriendly chemicals and fluid additives for exploration and exploitation of oil and gas resources in onshore and offshore environments needs the development and/or identification of novel HSE-friendly chemicals and additives to improve operational excellence and safeguard the global environment. Hence, a suite of novel HSE friendly lubricants have been developed for exploration and exploitation of oil and gas resources without causing any damage and degradation to other marine and terrestrial resources. This paper describes the development, testing and evaluation of several HSE friendly lubricants that have been developed using waste cooking oil as the raw material. Physical and chemical processing of waste cooking oil available from the food and catering industry as a waste byproduct have led to the development of several HSE-friendly lubricants to be in the forefront of best drilling practices. Due to the green nature of the products, they will have positive impact on the workers' health, rig site safety, and the surrounding environment. Experimental results obtained by conducting industry standard lubricity tests indicate that the newly developed HSE-friendly lubricants have similar or better performance compared to the currently used equivalent lubricants and thus demonstrated their potential as the viable alternatives to equivalent commercial products. Due to the health, safety and environment-friendly nature of the newly developed lubricant products, they will ensure the exploration and exploitation of oil and gas resources with positive impact on the preservation of other marine and terrestrial resources and thus expected to safeguard the global environment and ecosystems. Due to the high potential of the lubricants to improve the interface lubrication of mating surfaces, they are expected to play an effective role in mitigating the torque and drag in deviated, horizontal, extended reach, multilateral and also vertical wells with high dogleg severity while drilling, pulling and running the drill string into the wellbore.
Nanofluid, an emerging heat transfer fluid, is nowadays considered a new field of scientific research that could strengthen the thermal and mechanical properties of the base fluid. Nanosized particles of metal, alloy, and other high conductive material are mixed with engine lubricants to alleviate friction and wear. The purpose of the project is to experimentally assess the feasibility of using Nano-fluid lubricant in IC engine. Nano-sized Copper particles are mixed with the oil engine to enhance the performance of the heat transfer. The present study postulated that adding a nano-additive to the oil is a key factor for enhancing the thermal performance of the internal combustion engine. In particular, the experiments implemented in the study concentrate on the engine oil temperature, the gases exhaust temperature, and the performance of the cooling system. It has been shown that adding nanoparticles at 3 % VOF inside the oil engine, has reduced the temperature up to 26% of engine surface and 16% of the oil engine. The performance of the cooling system, presented by demonstrating the exit temperature of the radiator coolant, has shown to be slightly enhanced due to the augment in the thermal conductivity of the mixture. Heat losses for lubricant to the environment has dropped by 17% while the engine break thermal efficiency enhances by a factor of 1.5.
There are many types of equipment failures encountered during the operation of oil-flooded twin screw natural gas compressors. Defining the failure modes of gas compressors mining sour gas is of primary importance for improving reliability. The failure modes for compressors operating with hydrodymanic journal bearings are different from compressors operating with rolling element bearings. Gas compressors operating in corrosive environments easily succumb to failures such as corrosion-pitting, hydrogen-assisted fatigue and chemical attack. Some common failure modes will be defined for each type of bearings used in rotary screw compressors. Identifying these failure modes assists in defining the problem so that new lubricants can be designed to extend the working life of the compressor.
The failure modes of roller bearing equipped compressors operating in sour and acid gases are primarily due to premature spall formation from hydrogen-assisted fatigue (i.e. hydrogen embrittlement) and sulfide stress corrosion. We have found that hydrodynamic journal bearings equipped compressors operating in sour gases will fail due to sulfide corrosion attack of the hydrodynamic bearings. A new additive system was developed to inhibit both types of failure modes. Laboratory corrosion tests were used to compare corrosion inhibition of new additive system to well-established compressor lubricants. When levels of corrosion inhibition were established, the experimental lubricants were field tested. Field tests of this experimental lubricant were carried out in compressors operating with both hydrodynamic bearings and rolling element bearings. The testing in this difficult natural gas field, demonstrated that CPI’s new experimental fluids have extended the operating time to failure, for compressors operating with both type of bearing systems, from about 2,000 hours to well over 10,000 hours. CPI has developed lubricant solutions that improve the reliability by extending the time to failure for oil-flooded twin screw compressors mining water-saturated natural gas streams with both acid gas and sour gas elements.
The use of invert emulsion drilling fluids as a key enabler to successfully drill extended reach wells and access hydrocarbons that were previously out of reach has been common practice across the industry for decades. One of the more recent, but less frequently discussed, topics is how to effectively design a solidsfree, brine-based completion fluid to facilitate the running of the completion by reducing torque and drag. The choice of lubricant for brine-based completion fluids is primarily driven by technical performance, both in terms of torque reduction and compatibility with the brine, potential brine contaminants, such as divalent ions, invert emulsion drilling fluid, and crude oil that may be encountered in the field. During the planning phase for a recent ultra-extended-reach drilling campaign located offshore Sakhalin Island, it was highlighted that, without a lubricant in the completion brine, neither the upper nor the lower completion would be able to reach the required total depth, based on historical friction factor data. The brine planned for use as a completion fluid must demonstrate lubricity features near that of an invert-emulsion drilling fluid for the well to be completed successfully. This paper summarizes the laboratory test results to validate the lubricant selection and provides details about the operational procedures and results achieved after using the new lubricant in the field for the first time.