Simulation of Pressure Pulses in Top-hole Cementing Operations

Denne masteroppgaven undersøker utviklingen av trykkpulser i topphullseksjoner, frembrakt fra utstøting av sementplugger under sementeringsoperasjoner. Topphull refererer i denne sammenheng til de øverste seksjonene av en brønn, som blir boret uten utblåsningssikring og marint stigerør. Målet med oppgaven har vært å utforske trykkpulsfenomenet og evaluere størrelsen av trykket i borehullet. I tillegg har fokus blitt rettet mot design faktorer ved topphullsystemet og hvordan disse påvirker energitapet til den forplantende trykkpulsen. Fenomenet, som ikke er mye omtalt i litteraturen, kan potensielt forårsake skade på formasjon og på havbunnsinstallert boreutstyr. Økt kunnskap på dette feltet er derfor av stor interesse. Tilnærmingen for å utforske fenomenet har vært å konstruere en digital modell av topphullsystemet, og deretter utføre simuleringer av trykkutvikling for flere ulike tilfeller. En grunnleggende studie av bore- og sementeringsoperasjoner i topphullseksjoner, har blitt utført for å skape et solid fundament for den digitale modellen. Dette teoretiske fundamentet blir presentert i to ulike kapitler. Det første beskriver grunnleggende metoder og utfordringer ved bore- og sementeringsoperasjoner i topphullseksjoner, men også grunnleggende teori for trykkbølger og trykkpulsfenomenet. Det andre kapitlet beskriver oppsettet og applikasjonene til et stigerørsfritt system for returnering av boreslam, som ble implementert i modellen. Den digitale modellen ble konstruert i Matlab R2020a ved bruk av verktøypakken Simscape Fluids. Hensikten med modellen var å få tilgang til verdifull kunnskap om trykkpulsfenomenet. En detaljert beskrivelse av modellen blir presentert med forklaringer av nøkkelkomponenter, antakelser, grunnleggende ligninger og ikke-newtonske reologimodeller. De utførte simuleringene gav verdier for trykk i borehullet og for energitap forårsaket av komponenter i systemet. Ifølge de simulerte resultatene, så vil formasjonen i bunnen av borehullet bli utsatt for et ekstra trykk på 10,21 – 18,54 bar fra pulsen, avhengig av systemets design. I tillegg indikerer resultatene at 65,2 – 82,0% av det totale energitapet blir forårsaket av tilbakeslagsventilene i foringsrøret. Videre arbeid anbefales for å øke graden av troverdighet for de simulerte resultatene. Hovedfokuset i dette arbeidet bør rettes mot forbedringer av fluidsystemets grensebetingelser og modellering av tilbakeslagsventiler. Anbefalte løsninger for dette formålet er evaluering av alternative simuleringsprogrammer og søk etter forbedret kunnskap gjennom eksperimenter eller ved informasjon fra industrien.This thesis investigates the development of pressure pulses from launching the wiper plugs in top-hole cementing operations. In this context, top-hole refers to the uppermost sections of a well, which is drilled without the blow out preventer and marine drilling riser installed. The objective has been to explore the phenomenon and evaluate the magnitude of downhole pressure. In addition, focus has been directed towards design characteristics of the top-hole system and how these parameters affect the energy loss of the propagating pressure pulse. The phenomenon, which is not much discussed in literature, can potentially cause damage to the formation and to subsea installed drilling equipment. Therefore, increased knowledge on the topic is of great interest. The approach for exploring the phenomenon has been to construct a digital model of the tophole system, and then perform simulations of pressure development for several different cases. A study on fundamental characteristic of top-hole drilling and cementing operations has been conducted to provide a solid fundament for the digital model. This theoretical fundament is provided in two separate chapters. The first one describes basic methods and challenges found in top-hole drilling and cementing operations, but also basic theory on pressure waves and the pressure pulse phenomenon. The second one describes the setup and applications of a riserless mud recovery system, which was implemented in the digital model. The digital model was built in Matlab R2020a by use of the Simscape Fluid tool package, with the intention of accessing valuable knowledge on the pressure pulse phenomenon. A detailed description of the model is provided, with explanations of key components, assumption, fundamental equations and non-Newtonian rheology models. The simulations provided values for the downhole pressure and for the energy losses across system components. Simulated results state that the bottom hole formation will be exposed to an additional pressure of 10,21 - 18,54 bar from the pulse, depending on the system design. In addition, results indicate that 65,2 – 82,0% of the total energy loss is taken across the float valves in the shoe track. It is recommended that further work is invested to increase the level of confidence for the simulated results. The main focus in this work should be directed towards improvement of fluid system boundary conditions and float valve representation. Recommended solutions for this purpose are evaluation of alternative simulation software’s and search for improved knowledge through experimental activities or through information from the industry

Perspective Review on Subsea Jet Trenching Technology and Modeling

This paper presents a comprehensive review on subsea jet trenching technology via a critical analysis of its principle, mechanism, devices, modeling approaches, as well as properties of subsea sediments. This review shows that the success of jet trenching operations is closely related to some key factors including the soil conditions, trencher specifications, and characteristics of pipelines or cables. Three case histories are presented to demonstrate the importance of these key factors and their interrelationships. This paper also points out a number of challenges pertaining to the implementation of the jet trenching method in carbonate sediments, as well as some limitations and gaps in the existing modeling approaches. Future perspective researches that are recommended to develop: (1) promising theories, like turbulent submerged flow, and (2) robust numerical approaches, such as the smoothed particle hydrodynamics (SPH) and material point method (MPM) to substantiate the experimental experience and reveal possible hidden mechanisms. Document type: Articl

Advanced Mud System for Microhole Coiled Tubing Drilling

An advanced mud system was designed and key components were built that augment a coiled tubing drilling (CTD) rig that is designed specifically to drill microholes (less than 4-inch diameter) with advanced drilling techniques. The mud system was tailored to the hydraulics of the hole geometries and rig characteristics required for microholes and is capable of mixing and circulating mud and removing solids while being self contained and having zero discharge capability. Key components of this system are two modified triplex mud pumps (High Pressure Slurry Pumps) for advanced Abrasive Slurry Jetting (ASJ) and a modified Gas-Liquid-Solid (GLS) Separator for well control, flow return and initial processing. The system developed also includes an additional component of an advanced version of ASJ which allows cutting through most all materials encountered in oil and gas wells including steel, cement, and all rock types. It includes new fluids and new ASJ nozzles. The jetting mechanism does not require rotation of the bottom hole assembly or drill string, which is essential for use with Coiled Tubing (CT). It also has low reactive forces acting on the CT and generates cuttings small enough to be easily cleaned from the well bore, which is important in horizontal drilling. These cutting and mud processing components and capabilities compliment the concepts put forth by DOE for microhole coiled tubing drilling (MHTCTD) and should help insure the reality of drilling small diameter holes quickly and inexpensively with a minimal environmental footprint and that is efficient, compact and portable. Other components (site liners, sump and transfer pumps, stacked shakers, filter membranes, etc.. ) of the overall mud system were identified as readily available in industry and will not be purchased until we are ready to drill a specific well

Characterization of a Dipole Flow System Using Point Velocity Probes

A direct groundwater velocity measurement tool, the Point Velocity Probe, was developed to measure velocities in the vertical and horizontal directions. The tool was designed and tested in a low-cost laboratory flow-through tank. Following testing, the tool was deployed in the field surrounding a dipole well used to conduct an aquifer tracer test. The velocity data showed some deviations from modeled behavior and was used to characterize the heterogeneity of the aquifer. The results from the flow and transport modeling suggest that the area very close to the well was extremely important to the behavior of tracers in the dipole flow system. Finally, a simple model was developed to optimize hydraulic conductivity using the velocity data with good results

Advanced Ultra-High Speed Motor for Drilling

Three (3) designs have been made for two sizes, 6.91 cm (2.72 inch) and 4.29 cm (1.69 inch) outer diameters, of a patented inverted configured Permanent Magnet Synchronous Machines (PMSM) electric motor specifically for drilling at ultra-high rotational speeds (10,000 rpm) and that can utilize advanced drilling methods. Benefits of these motors are stackable power sections, full control (speed and direction) of downhole motors, flow hydraulics independent of motor operation, application of advanced drilling methods (water jetting and abrasive slurry jetting), and the ability of signal/power electric wires through motor(s). Key features of the final designed motors are: fixed non-rotating shaft with stator coils attached; rotating housing with permanent magnet (PM) rotor attached; bit attached to rotating housing; internal channel(s) in a nonrotating shaft; electric components that are hydrostatically isolated from high internal pressure circulating fluids ('muds') by static metal to metal seals; liquid filled motor with smoothed features for minimized turbulence in the motor during operation; and new inverted coated metal-metal hydrodynamic bearings and seals. PMSM, Induction and Switched Reluctance Machines (SRM), all pulse modulated, were considered, but PMSM were determined to provide the highest power density for the shortest motors. Both radial and axial electric PMSM driven motors were designed with axial designs deemed more rugged for ultra-high speed, drilling applications. The 6.91 cm (2.72 inch) OD axial inverted motor can generate 4.18KW (5.61 Hp) power at 10,000 rpm with a 4 Nm (2.95 ft-lbs) of torque for every 30.48 cm (12 inches) of power section. The 6.91 cm (2.72 inch) OD radial inverted motor can generate 5.03 KW (6.74 Hp) with 4.8 Nm (3.54 ft-lb) torque at 10,000 rpm for every 30.48 cm (12 inches) of power section. The 4.29 cm (1.69 inch) OD radial inverted motor can generate 2.56 KW (3.43 Hp) power with 2.44 Nm (1.8 ft-lb) torque at full speed 10,000 rpm for every 30.48 cm (12 inches) of power section. Operating conditions are 300 voltage AC at the motor leads. Power voltage losses in the cables/wirelines to the motor(s) are expected to be about 10% for 5000 feet carrying 2 amperes. Higher voltages and better insulators can lower these losses and carry more amperes. Cutting elements for such high tip velocities are currently not available, consequently these motors will not be built at this time. However, 7.62 cm (3 inch) OD, low speed, PMSM radial electric motors based on this project design are being built under a 2006 Oklahoma Center for the Advancement of Science and Technology 'proof of concept' grant

Through Tubing Well Abandonment: Challenges and Possibilities

Well abandonment is crucial in the oil and gas industry, ensuring environmental safety and compliance as wells cease production. Through Tubing Abandonment (TTA) is an innovative approach that differs from traditional plug and abandonment (P&A) methods by allowing operations to be conducted through existing tubing, thereby eliminating the need for its removal. This method offers significant economic benefits and reduces Health, Safety, and Environment (HSE) risks. This thesis examines the effectiveness, challenges, and possibilities of TTA. Through a comprehensive review of industry reports and a qualitative interview with a field professional, the study explores the operational efficiencies, cost savings, and technological advancements required for TTA. The findings demonstrate that TTA can lead to substantial cost reductions and time savings while maintaining well integrity and environmental safety. Key challenges include the need for advanced logging tools and reliable cement placement techniques. The study highlights the potential of new sealing materials and improved logging technologies to overcome these barriers. Regulatory compliance and strategic planning are essential for optimizing TTA outcomes. The conclusion synthesizes the research findings, providing a detailed overview of TTA's benefits and limitations. It also offers insights into TTA's future, emphasizing the importance of technological innovation and regulatory adaptation in enhancing well abandonment practices in the oil and gas industry.Well abandonment is crucial in the oil and gas industry, ensuring environmental safety and compliance as wells cease production. Through Tubing Abandonment (TTA) is an innovative approach that differs from traditional plug and abandonment (P&A) methods by allowing operations to be conducted through existing tubing, thereby eliminating the need for its removal. This method offers significant economic benefits and reduces Health, Safety, and Environment (HSE) risks. This thesis examines the effectiveness, challenges, and possibilities of TTA. Through a comprehensive review of industry reports and a qualitative interview with a field professional, the study explores the operational efficiencies, cost savings, and technological advancements required for TTA. The findings demonstrate that TTA can lead to substantial cost reductions and time savings while maintaining well integrity and environmental safety. Key challenges include the need for advanced logging tools and reliable cement placement techniques. The study highlights the potential of new sealing materials and improved logging technologies to overcome these barriers. Regulatory compliance and strategic planning are essential for optimizing TTA outcomes. The conclusion synthesizes the research findings, providing a detailed overview of TTA's benefits and limitations. It also offers insights into TTA's future, emphasizing the importance of technological innovation and regulatory adaptation in enhancing well abandonment practices in the oil and gas industry

Concept study of slurry lifting from deep sea mining in an arctic environment

Ved store havdyp finnes det mineral- og metallrike avsetninger. Flere av disse metallene brukes i dagens teknologi for produksjon og lagring av fornybar energi. Videre er det forventet en økning i etterspørselen av metallene brukt i teknogi forbundet med det grønne skiftet. Midhavsrygger forbindes ofte med hydrotemale skorsteiner og de stabile forholdene rundt midthavsrygger tillater at det over tid kan samles opp store avsetninger av massive sulfider, også referert til som SMS (Seafloor Massive Sulphides) som felles ut av væsken som kommer ut av skorsteinene. Norge har suverenitet over en del av den nordlige Midtatlantiske ryggen i forbindelse med suverenitet av Jan Mayen og Spitsbergen er noen av disse områdene interessante for undersjøisk guvedrift. I tilegg er det bekreftet flere aktive skorsteiner med tilhørende SMS avsteninger i disse områdene. En teknisk utfordring med å hente ut disse mineralene fra havdyp på 800-5000 meters dyp er å løfte den brutte malmen til overflaten. Dagens løsning med å løfte malmen er å bruke en stiv riser som henger fra et produksjonsfartøy i overflaten, mens malmen løftes ved hjelp av en nedsenkbar pumpe som pumper opp malmen som en slurry til produksjonsfartøyet. En ulempe med denne løsningen er at den ikke tåler store værlaster, for eksemper bølger, som er vanlige i arktis. Denne masteroppgaven består av et konseptuelt design av et løftesystem som kan brukes i arktiske strøk. Designet er basert på en litteraturstudie og designet er evaluert ved hjelp av en FMECA (Feil Moduser Effekt og Kritikalitets Analyse, "Failure Modes Effects and Criticality Analysis"). Design studien ble avgrenset til løfting av en slurry, hvor slurryen blir sendt inn til systemet ferdig blandet med sjøvann i et fleksibel rør. Et resultat av FMECAen er hvilken komponent som er mest kritisk for svikt. Fokuset i denne FMECAen var teknisk svikt og estimat av påfølgende nedetid. Det er ikke blitt foretatt et detaljert design av det foreslåtte konseptet, men en mulighetstudie av ulike konsepter. Grunnet denne mangelen av detaljer har ikke detaljerte dimensjoner blitt etablert og kostnadsestimat er ikke utført. Det foreslåtte designet er en hybrid riser løsning som står på havbunnen og er koblet til overflatefartøyet ved hjelp av et fleksibelt stigerør. Slurrien blir løftet ved hjelp av en fortregningspumpe drevet av trykksatt returvann. Dette konseptet frigjør stigerøret fra overflatefartøyets bevegelser, men stigerøret blir da ikke mobilt. En konsekvens av dette er at det er et større behov for infrastruktur på havbunnen. Men dette kan gi muligheten for å skape en løftesentral for flere mindre felt. En mulighet med en slik sentral er at en kan samle ressuser som trengs for undervanns sørvis. Hammerfest ble valgt som logistikk havn for operasjonen og har en seilings avstand på circa 616 kilometer fra Lokeslottet. Det ble antatt en uplanlagt mobilsering av et skip med last vil ta fem dager til det er på plass ved Lokeslottet. Dette ble brukt til estimat av uplanlagt nedetid. En observasjon av dette var at det å ikke ha deler, utstyr eller personell tiljengelig ved behov kan medføre mye ekstra nedetid. For å unngå ikke planlagt nedetid kan det være lurt å bruke tilstandovervåkning til å overvåke tilstanden på installert utstyr, slik at nødvendig vedlikehold kan bli utført ved planlagte stans. FMECAen endte med 106 feilmoduser, den mest kritiske feilen var utmatting i "slurry pipe". Noen flere feil er vurdert i diskusjonsdelen. Flere frekvensestimater og nedetidsestimater er hentet fra "OREDA 2015 subsea equipment reliability handbook". Hvor overførbare pålitlighetsdataene er til undersjøisk gruvedrift er uvisst, men det er en av få tiljengelige åpne pålitlighetsdatabaser. Det er lite data å sammenligne resultatene i FMECAen med, så en validering av disse resultatene var ikke mulig. Til videre arbeid er det foreslått å utføre et mer detaljert design slik at et skikkelig grundighetstudie kan utføres, et videre studie i å bruke en riser kollektivt til løfting fra flere felt og se på hvilken størrelse på avsetningene som er av interesse.In the deep sea there are deposits that can contain large volumes of high-grade ore containing minerals and metals used in new renewable energy technology. A boost in the demand for these metals are expected to increase due to focus towards the green energy transition. Mid ocean spreading ridges are often associated with hydrothermal vents, that can accumulate significant Seafloor Massive Sulphide (SMS) deposits, due to the stable conditions allowing for long-lived venting activity. Metals are also found in polymetallic nodules, metal-rich crusts and as rare-earth elements (REE). Norway has sovereignty of a part of the northern Mid-Atlantic Ridge, where hydrothermal vents and SMS deposits are confirmed. A technical challenge of extracting minerals from deep waters (800-5000 meters) is to lift the ore from the seabed to the surface. The current state-of-the-art lifting systems consists of a riser hanging off the production vessel and utilises a submersible pump to lift the slurry to the surface vessel. A limitation of this design is that it cannot be operated during harsh environmental conditions, like in the arctic. This thesis consists of a conceptual design study of a lifting system suitable for arctic environments. The design is based on a literature review and an evaluation of this design by the use of a Failure Modes Effects and Criticality Analysis (FMECA). The design was limited to slurry lifting, where the slurry enters the system premixed with seawater delivered by a flexible jumper. The goal of the FMECA is to expose the most critical components in the design. The main focus of the FMECA has been towards the operational phase and the possibilities for maintenance and rough downtime estimates. There has not been a detailed design of the suggested system, more an exploratory study of the possible concepts. Due to this lack of detail there are no detailed dimensions and economic estimates. The final suggested design is a hybrid riser configuration, standing on the seabed and connected to the surface vessel by a flexible jumper. The slurry is lifted by the use of a positive displacement pump, powered by the pressurised return water of the slurry. This concept decouples the riser from the motions of the surface vessel, but the riser is stationary. A consequence of this is that more bottom infrastructure is needed as a field expands, but this also opens up for new possibilities; a central lifting hub serving several smaller fields and the hub can host several subsea service capabilities. Hammerfest was the harbour of choice as the logistics harbour. It is a town located on the Norwegian mainland and has approximately 616 km sailing distance to the sites along the northern Mid-Atlantic Ridge where hydrothermal vents and SMS deposits are confirmed. It is assumed it will take five days for an unplanned mobilisation of a vessel to deliver goods. This was used to estimate downtime. A conclusion from this exercise was that the logistics of the operations are important, and the potential wait of lacking spares, equipment or personnel can lead to serious extensions to unplanned downtime. To avoid unplanned downtime it is important to monitor the state of the equipment used. The tools for data assisted condition monitoring can be helpful to track the degradation of the monitored equipment and one can perform preventive maintenance on the degraded equipment during the planned maintenance cycles. The FMECA resulted in 106 failure modes and the most critical component was the slurry pipe failing due to fatigue. A few selected failures are selected for the discussion. Some of the frequency estimates and repair time estimates was selected from the OREDA 2015 subsea equipment reliability data handbook. The true match of the reliability data is uncertain, but this is one of the few available offshore reliability databases. The focus of the FMECA was mainly towards technical failures, resulting in downtime due to repair and some failures due to environmental spillages. There are little data to compare the results with and one is unable to check the validity of these results. For further work it is suggested to complete a more detailed design to check technical feasibility, and to explore the use of a collective lifting hub further to see what size deposits are of interest

Removal of Sustained Casing Pressure by Gravity Displacement of Annular Fluid

Sustained Casing Pressure (SCP) is the undesirable casing head pressure of a well annulus that rebuilds when bled-down. As the conventional methods for SCP removal using rigs are expensive, there is a need for improvement. Annular intervention for replacing the fluid above the leaking cement with a heavier fluid to stop gas migration is a solution for SCP removal; however, previous attempts failed due to miscibility of injected fluids. Using hydrophobic heavy fluids for the purpose is a newly proposed technique to the technology. Potential of theoretically selected and produced immiscible heavy fluids are investigated in characterized annular fluids. A transparent laboratory scaled-down hydraulic analog of well’s annulus provided visual evidence for displacement geometry and did the first stage testing of heavy fluid injection into clear synthetic-clay muds. A 20-foot physical model then tested the performance of the displacement process. Settling of various heavy fluids with densities from 11 to 23 ppg in drilling fluids with densities from 9 to 13 ppg provided quantitative bottom pressure data. Finally, a full-size test in 2750-foot well examined the viability of the technology. Visualization experiments proved that the counter-current flow in annulus leads to up-lifting of heavy fluid droplets and must be minimized for a desirable displacement process. Selection of injection geometry and rate are also essential to maintain a controlled transport of heavy fluid downwards. Pilot experiments developed mathematical correlations relating the process performance to fluid properties and rate. Full-size test shows that hydrophobic heavy fluids are able to slip in long columns; however, bridge-over of buoyant settling may occur due to high injection rates and/or flotation effect of migrating gas that was entrapped in annular fluid. The findings in this research present solid support to the viability of immiscible gravity displacement of annular fluid for remediating a well annulus affected with SCP. For given fluid properties and in confined annular space, injection rate is the key to a successful displacement. Finally, the research proved that the duration of a complete displacement process and required heavy fluid volume are inversely correlated. For any operation design; time and killing material restrictions must be considered

SeisCORK engineering design study

The goal of SeisCORKs is to make simultaneous and co-located seismic, pressure, temperature, pore water chemistry and pore water biology measurements in the seafloor. We want to see the small events in the vicinity of the borehole for three reasons: 1) After an event fluid may flow in the formation in response to the changing stress regime. Down to what magnitude of event do the pressure transients in the well respond? 2) Fluid flow causes small earthquakes. One mechanism for example is by changing the temperature of the rocks which expand and contract, altering the stress regime. We want to look for this fluid flow. 3) Laboratory studies of rock deformation show that shear fracture is preceded by the coalescence of interacting tensile microcracks which are observed as “acoustic emissions”. By placing high frequency geophones next to faults it may be possible to observe these “acoustic” precursors to rock failure. Since in reservoirs on land small events appear in the frequency band 400-800Hz, no one has yet tried to observe them in oceanic crust. SeisCORKs also obviate the considerable logistical, administrative, and clearance difficulties associated with scheduling a shooting ship to run offset VSPs. We resolved to start with a “tubing conveyed” SeisCORK configuration consisting of four three-component sondes at 50m separation lowered on the outside of 4.5in casing (or drill pipe) inside 10-3/4in casing.Funding was provided by the National Science Foundation under Contract Nos. OCE-0221832 and OCE-0450318