Drilling Phase Research Articles

Quantification of Wellbore-Collision Probability by Novel Analytic Methods

Summary Unintentional collision between two wellbores may have serious economic and health, safety, and environmental consequences. It is therefore important to evaluate the probability of such an event in the well-planning phase and at critical stages during the drilling phase. A commonly used approach is to analyze the collision probability between two points, one in each wellbore, which are determined from geometric criteria only. This procedure may ignore point pairs with higher collision probabilities, and thereby lead to overoptimistic conclusions. Typically, the results from such methods will be accurate only for simple wellbore geometries, such as straight sections, and for position uncertainties that are highly symmetrical with respect to the wellbores. More advanced methods that overcome such limitations are impractical for general application because of high conceptual or computational complexity. This paper proposes novel analytic methods that may potentially overcome these problems. Formulae are derived for two important situations: the direct-hit (DH) and the unintentional-crossing (UC) scenarios. In both cases, the spatial region of interest is divided into carefully designed segments, such that the collision probability can be accurately evaluated for each segment. The total collision probability is then found by summing the results over all segments. The main advantage of this approach is that it gives accurate results for arbitrary well geometries and uncertainty-ellipsoid orientations. The algorithms can easily be integrated in existing software for wellbore-anticollision analysis. The paper shows examples of results that are all in good agreement with control calculations. Compared with existing methods, the proposed methods are therefore believed to represent an improvement to quantitative collision-probability analysis for both the wellbore-planning and the drilling phases.

Real‐Time Earthquake Monitoring during the Second Phase of the Deep Fault Drilling Project, Alpine Fault, New Zealand

ABSTRACT The Deep Fault Drilling Project (DFDP) is a multinational scientific drilling effort to study the evolution, structure, and seismogenesis of the Alpine fault, New Zealand, via in situ measurements of fault rock properties. The second phase of drilling (DFDP‐2), undertaken in the Whataroa Valley in late 2014, was intended to intersect the Alpine fault at a depth of around 1 km. In conjunction with the drilling and on‐site science activities, a real‐time seismic monitoring scheme and traffic‐light response protocol were established to detect, locate, and if necessary respond to seismicity within 30 km of the drill site. This network was operated around the clock between late August 2014 and early January 2015, and we detected and located 493 earthquakes of M L 0.6–4.2. None of these earthquakes occurred within 3 km of the drill site, and nor did any of the seismicity detected require changes to drilling operations. The monitoring was undertaken using open‐source software operated by an international team of 16 seismologists (including eight postgraduate students) working in 7 institutions and 3 countries to provide rapid on‐ and off‐site manual checking and relocating of events. The team’s standard response time between detection and final location was less than 30 min under normal background seismicity conditions and up to 1 hr during swarm activity and for low‐priority, distant (≥30 km epicentrally from the drill site) earthquakes. This article documents the methodology, infrastructure, protocols, outcomes, and key lessons of this monitoring.

A punctuated Late Ordovician and early Silurian deglaciation and transgression: Evidence from the subsurface of northern Saudi Arabia

ABSTRACT The lower section of the lower Silurian Qusaiba Member, Qalibah Formation, is characterized by regionally developed organic-rich shales that have sourced many of the large Paleozoic petroleum systems of Saudi Arabia. In northern Saudi Arabia, these high–total organic carbon (TOC) horizons are being assessed for their unconventional shale-gas potential. The initial phase of exploration drilling, which resulted in a quadrupling of the number of penetrations in northern Saudi Arabia, had the dual purpose of (1) assessing the high-TOC horizons as an unconventional resource play and (2) acquiring the fundamental data required to understand the geologic development of the zones of interest within the lower Qusaiba. The availability of numerous new cores from across northern Saudi Arabia enabled an extensive refinement of the existing biostratigraphy and enhanced integration between graptolite and palynomorph biozonation systems. In cores from the study area, four distinct sedimentary facies are recognized, (1) pyritic siltstone, (2) black mudstone, (3) black chert, and (4) gray shale, representing distinct paleoenvironmental conditions related to the stepped latest Ordovician and early Silurian Gondwanan deglaciation. The failure of the Gondwanan ice sheet was not a simple, short-lived, consistent melting and associated flooding of a flat continental shelf. This study highlights the complex interplay of sea-floor topography, ocean currents, sediment supply, and variations in the rate of melting of the ice sheet. With the associated rising ambient temperatures there are (1) increasing clay concentrations associated with intensifying chemical weathering of the exposed land mass and (2) progressive lowering of the carbonate compensation depth as water temperatures rise, enabling the preservation of carbonate shell material.

Pre-operative Screening and Manual Drilling Strategies to Reduce the Risk of Thermal Injury During Minimally Invasive Cochlear Implantation Surgery.

This article presents the development and experimental validation of a methodology to reduce the risk of thermal injury to the facial nerve during minimally invasive cochlear implantation surgery. The first step in this methodology is a pre-operative screening process, in which medical imaging is used to identify those patients that present a significant risk of developing high temperatures at the facial nerve during the drilling phase of the procedure. Such a risk is calculated based on the density of the bone along the drilling path and the thermal conductance between the drilling path and the nerve, and provides a criterion to exclude high-risk patients from receiving the minimally invasive procedure. The second component of the methodology is a drilling strategy for manually-guided drilling near the facial nerve. The strategy utilizes interval drilling and mechanical constraints to enable better control over the procedure and the resulting generation of heat. The approach is tested in fresh cadaver temporal bones using a thermal camera to monitor temperature near the facial nerve. Results indicate that pre-operative screening may successfully exclude high-risk patients and that the proposed drilling strategy enables safe drilling for low-to-moderate risk patients.

Design of the ROV Dedicated Seafloor Heat Flow Probe

As the exploration of the natural gas hydrate is developed towards the target drilling phase, the traditional EWING-type and LISTER-type heat flow probe is unable to meet the needs of fine detection of the seafloor heat flow in the target area of the nature gas hydrate. The ROV (Remotely Operated Vehicle) dedicated seafloor heat flow probe is designed based on the status and operating characteristics of ROV which has been already adopted in China, which is suitable for measuring the large-scale and high-density seafloor in-situ heat flow, analyzing and understanding the fine thermal structure and thermal state of the special geological structure, and focusing on solving seafloor heat flow measurements in local structure. In the ROV dedicated seafloor heat flow probe, a high-precision NTC thermistor is adopted as the sensor, and ADUC845 chip with an internal integration of 24-bit high-resolution A/D converter is selected as the main processor. Furthermore, the ROV (Remotely Operated Vehicle) dedicated seafloor heat flow probe can measure the resistance values of the thermistors in five channels through the measurement mode of DC unbalanced bridge in a way of time sharing, and use STEINHART & HART equation to conduct R-T conversion, thus obtaining a more accurate geothermal gradient curve of the seafloor sediments after correction by the seven-point three-phase data conversion method, of which the measurement accuracy is 0.005℃ and the resolution ratio reaches 0.001℃. And it can also obtain the valuable raw data of the heat flow with the sea trial of the “SeaLion ROV” of Chinese scientific investigation vessel “Ocean VI” and the “Jiaolong HOV (Human-Occupied Vehicles)” of “Xiangyanghong XVI” vessel.

Measurement of platform conductor preload in streamlining the life extensions of ageing offshore wells

The life extension of ageing oil wells is becoming an ever more crucial part of an operator's activities in recent years, mainly due to slumping oil price which discourages new exploration and the potential extended operation of some older fields with sufficient producing capacity still remaining. The conductor forms one of the primary structural components of wells and its deterioration over time warrants immediate integrity assessment and rehabilitation plans. The construction residual loading or preloads on the conductor are calculated as per standard guidelines and by analytical means during its design and installation phase, but may not be realistic when assessing aged conductors, due to the high levels of over-conservatism built in to address the various uncertainties during the well drilling phase, hence a more practical means of evaluating this residual load is required in carrying out the integrity assessments. This article presents the novel use of ultrasonic based non-destructive technique (NDT) to measure the conductor preload by observing the travel time of the longitudinal critical refracted (LCR) waves and employing the acoustoelastic method to determine the structural stresses. The measurement of the time of flight (TOF) of this wave component is evaluated from the signals measurement under a range of preload stresses induced into the specimen, and the acoustoelastic calibration curve is obtained as a result, for various section geometries and dimensions. Numerical analyses are also carried out to correlate and validate the magnitude order of the acoustoelastic constant of typical conductor steel grade (grade-B). These are in good agreement with each other and can be a very reliable tool for the on-site preload measurements during oil well integrity assessment. This measurement of conductor preload results in minimising any associated uncertainties, assumptions and the corresponding over-conservatisms carried over from the design stage, hence streamlining the repair and rehabilitation strategies to the most critical well-conductor groups in the field, thus significantly reducing the costs and resources for operators in extending life of aged wells.

Microwave drying remediation of petroleum-contaminated drill cuttings

The oil reservoir drilling phase generates contaminated cuttings with oil formation itself. These cuttings must be subjected to a decontamination process before being disposed of in the environment. Several technologies are cited in literature for the remediation of soil contaminated with oil or diesel, but none have been reported to remedy drill cuttings contaminated with oil from reservoir. The reservoir drill cuttings are a problem because its discharge is not allowed. The drying technology using microwave has shown promise in the decontamination of cuttings with non-aqueous base drilling fluid, conciliating good robustness and high removal efficiency. Considering the aspects mentioned previously, the application of heating and drying technology using microwave in the remediation of oil contaminated cuttings from well drill was studied. The influence of temperature, specific energy and initial content of water in the drying operation of the reservoir cuttings and of the drilling cuttings artificially contaminated with oil were analyzed. The results showed an influence of temperature in the drying of the cuttings, being necessary to reach the boiling temperature of heavier hydrocarbons to reach an efficient removal in the operation. The specific energy has a strong influence, reaching a total decontamination using 2.67 kWh/kg. The initial water content was effective in removing oil, reducing the residual level of oil with the increase of initial content of water. It also modifies the temperature profiles of the kinetic-warming of the contaminated cuttings. Both the technology and the equipment used proved effective for obtaining total decontamination of oil from the cuttings.

Environmental aspects of the geothermal energy utilisation in Poland

Geothermal energy is considered as a strategic and sustainable source of renewable energy that can be effectively managed in several economic sectors. In Poland, despite the abundant potential of such resources, its share in the energy mix of renewable energy sources remains insubstantial. The utilisation of geothermal resources in Poland is related to the hydrogeothermal resources, however, numerous researches related to petrogeothermal energy resources are being performed. The utilisation of each type of energy, including geothermal, has an impact on the natural environment. In case of the effective development of geothermal energy resources, many environmental benefits are pointed out. The primary one is the extraction of clean, green energy that is characterised by the zero-emission rate of pollutants into the atmosphere, what considering the current environmental pollution in many Polish cities remains the extremely important issue. On the other hand, the utilisation of geothermal energy might influence the natural environment negatively. Beginning from the phase of drilling, which strongly interferes with the local landscape or acoustic climate, to the stage of energy exploitation. It should be noted that the efficient and sustainable use of geothermal energy resources is closely linked with the current law regulations at national and European level.

Ten years of CO2 storage and operations

The CO2CRC storage research site, in the Otway Basin (south-west Victoria), focuses on understanding fundamental mechanisms of geological carbon storage resources in saline aquifers. The world-leading project is demonstrating that carbon capture and storage is a technically and environmentally safe way to make deep cuts into global greenhouse gas emissions. Upstream Production Solutions (Upstream PS) are the nominated site manager and have provided ongoing project management, facilities engineering, construction, operations and maintenance services to CO2CRC from the project’s inception. Over the course of the last 10 years, the project has undergone well and facilities design, and drilling and construction phases, with separate injections of over 80000 tonnes of CO2 rich gas into the formation for research purposes. Unique and dynamic concurrent projects as at the time of writing are: designing a fifth well for the project; commissioning a carbon capture package to provide valuable research data on emerging membrane and adsorption technologies; maintaining and monitoring the overall non-operational site; and planning for a well abandonment. This sphere of project activity across the whole life cycle requires a robust and holistic focus on management of risk, planning, implementation of right sized solutions and strong stakeholder communications. This paper details the nature of projects executed and specific challenges encountered and met whilst still following lean practices for a safe yet cost-effective operation for this world leading CO2 research project.

Application of Numerical Simulation for the Analysis of the Processes of Rotary Ultrasonic Drilling

Abstract Rotary ultrasonic machining (RUM) is a hybrid process that combines diamond grinding with ultrasonic machining. It is most suitable to machine hard brittle materials such as ceramics and composites. Due to its excellent machining performance, RUM is very often applied for drilling of hard machinable materials. In the final phase of drilling, the edge deterioration of the drilled hole can occur, which results in a phenomenon called edge chipping. During hole drilling, a change in the thickness of the bottom of the drilled hole occurs. Consequently, the bottom of the hole as a plate structure is exposed to the transfer through the resonance state. This resonance state can be considered as one of the important aspects leading to edge chipping. Effects of changes in the bottom thickness and as well as the fillet radius between the wall and bottom of the borehole on the stress-strain states during RUM are analyzed.

Soundscape analysis and acoustic monitoring document impacts of natural gas exploration on biodiversity in a tropical forest

Natural resource extraction is increasing rapidly in tropical forests, but we lag behind in understanding the impacts of these disturbances on biodiversity. In high diversity tropical habitats, acoustic monitoring is an efficient tool for sampling a large proportion of the fauna across varied spatial and temporal scales. We used passive acoustic monitoring in a pre-montane forest in Peru to investigate how soundscape composition and richness of acoustic frequencies varied with distance from a natural gas exploratory well and with operational phase (construction and drilling). We also evaluated how anuran and avian species richness and vocal activity varied with distance and between phases. Soundscape analyses showed that acoustic frequency similarity was greatest among sites closer to (≤250m) and farther from (≥500m) the platform. Soundscapes revealed more frequencies were used during construction and showed a weak trend of increasing frequency richness with increasing distance from the disturbance. Avian species richness and detections increased with distance from the platform, but anuran richness and detections declined with distance. Operational phase did not play a significant role in overall richness or activity patterns of either group. Among birds, insectivore detections increased with distance from the platform, and nectarivores were detected more frequently during the drilling phase. Results demonstrate that acoustic monitoring and soundscape analyses are useful tools for evaluating the impact of development activity on the vocalizing community, and should be implemented as a best practice in monitoring biodiversity and for guiding specific mitigation strategies.

IODP Expedition 337: Deep Coalbed Biosphere off Shimokita – Microbial processes and hydrocarbon system associated with deeply buried coalbed in the ocean

Abstract. The Integrated Ocean Drilling Program (IODP) Expedition 337 was the first expedition dedicated to subseafloor microbiology that used riser-drilling technology with the drilling vessel Chikyu. The drilling Site C0020 is located in a forearc basin formed by the subduction of the Pacific Plate off the Shimokita Peninsula, Japan, at a water depth of 1180 m. Primary scientific objectives during Expedition 337 were to study the relationship between the deep microbial biosphere and a series of ∼ 2 km deep subseafloor coalbeds and to explore the limits of life in the deepest horizons ever probed by scientific ocean drilling. To address these scientific objectives, we penetrated a 2.466 km deep sedimentary sequence with a series of lignite layers buried around 2 km below the seafloor. The cored sediments, as well as cuttings and logging data, showed a record of dynamically changing depositional environments in the former forearc basin off the Shimokita Peninsula during the late Oligocene and Miocene, ranging from warm-temperate coastal backswamps to a cool water continental shelf. The occurrence of small microbial populations and their methanogenic activity were confirmed down to the bottom of the hole by microbiological and biogeochemical analyses. The factors controlling the size and viability of ultra-deep microbial communities in those warm sedimentary habitats could be the increase in demand of energy and water expended on the enzymatic repair of biomolecules as a function of the burial depth. Expedition 337 provided a test ground for the use of riser-drilling technology to address geobiological and biogeochemical objectives and was therefore a crucial step toward the next phase of deep scientific ocean drilling.

Anthropogenic and natural methane emissions from a shale gas exploration area of Quebec, Canada

The increasing number of studies on the determination of natural methane in groundwater of shale gas prospection areas offers a unique opportunity for refining the quantification of natural methane emissions. Here methane emissions, computed from four potential sources, are reported for an area of ca. 16,500km2 of the St. Lawrence Lowlands, Quebec (Canada), where Utica shales are targeted by the petroleum industry. Methane emissions can be caused by 1) groundwater degassing as a result of groundwater abstraction for domestic and municipal uses; 2) groundwater discharge along rivers; 3) migration to the surface by (macro- and micro-) diffuse seepage; 4) degassing of hydraulic fracturing fluids during first phases of drilling. Methane emissions related to groundwater discharge to rivers (2.47×10−4 to 9.35×10−3Tgyr−1) surpass those of diffuse seepage (4.13×10−6 to 7.14×10−5Tgyr−1) and groundwater abstraction (6.35×10−6 to 2.49×10−4Tgyr−1). The methane emission from the degassing of flowback waters during drilling of the Utica shale over a 10- to 20-year horizon is estimated from 2.55×10−3 to 1.62×10−2Tgyr−1. These emissions are from one third to sixty-six times the methane emissions from groundwater discharge to rivers. This study shows that different methane emission sources need to be considered in environmental assessments of methane exploitation projects to better understand their impacts.

Method of Surface Interception To Access Annulus With Abnormal Gas Pressure

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper IPTC 18122, “A Safe and Efficient Method of Surface Interception To Access Outermost Sealed Annulus Charged With Abnormal Gas Pressure Relieves Well- Integrity Concerns,” by Prashun Kumar Das and Wael Moneer El-Mandrawy, Qatargas, prepared for the 2014 International Petroleum Technology Conference, Kuala Lumpur, 10–12 December. The paper has not been peer reviewed. One of the operator’s newly acquired ventures is in the North field offshore Qatar. Abnormal rise in Annuli C and D pressures during the last phase of drilling highlighted the need to investigate the condition of producing wells on other platforms. The chances of inner annuli becoming charged with shallow-gas pressure and possible communication to Annulus D was thought to be a well-integrity concern. Establishing safe access to the sealed and potentially gas-charged Annulus D thus posed a challenge. Introduction The North field is offshore northeast of Qatar and is the world’s largest nonassociated-gas field. The wells are typically 7-in. monobore completed with a 26-in. conductor and three casing strings. Wells are completed with a liner-top isolation packer, tied back to the surface with 7-in. corrosion-resistant-alloy tubing. The annuli between the well casings are labeled A (7×10¾ in.), B (10¾×13? in.), C (13?×18? in.), and D (18?×26 in.). Provisions were made for monitoring and bleeding off pressures in Annuli A, B, and C. Background During the drilling and well-completion phase, some of the wells developed unusual pressures in Annulus C. Attempts were made to bleed off gas through the drilling facility. However, pressures built up every time, indicating a continuous intrusion of gas. Further pressure bleedoff was not attempted because of concerns that it may open up the communication channels and aggravate the situation. Several attempts were then made to lubricate and fill Annulus C with treated brine, but these attempts did not help to subdue the gas pressure. A proposal was then made to operate the wells with modified maximum-allowable-annulus- surface-pressure and maximum-allowable- wellhead-operating-pressure techniques for Annulus C, considering it fully charged with gas. With time, it was established that the same wells also developed gas pressure in Annulus D.

The regional economic impact of oil and gas extraction in Texas

This paper empirically investigates the regional economic impact of oil and gas extraction in Texas during the recent shale oil boom. Regressions with county-level data over the period 2009–2014 support smaller multiplier effects on local employment and income than corresponding estimates drawn from popular input–output-based studies. Economic impacts were larger for extraction from gas wells than oil wells, while the drilling phase generated comparable impacts. Estimates of economic impacts are greater in a dynamic spatial panel model that allows for spillover effects across local economies as well as over time.

Combining airborne electromagnetic and geotechnical data for automated depth to bedrock tracking

Airborne electromagnetic (AEM) survey data was used to supplement geotechnical investigations for a highway construction project in Norway. Heterogeneous geology throughout the survey and consequent variable bedrock threshold resistivity hindered efforts to directly track depth to bedrock, motivating us to develop an automated algorithm to extract depth to bedrock by combining both boreholes and AEM data. We developed two variations of this algorithm: one using simple Gaussian or inverse distance weighting interpolators, and another using ordinary kriging and combined probability distribution functions of input parameters.Evaluation shows that for preliminary surveys, significant savings in boreholes required can be made without sacrificing bedrock model accuracy. In the case study presented, we estimate data collection savings of 1000 to 10,000NOK/km (c. $160 to $1600 USD/km) would have been possible for early phases of the investigation. However, issues with anthropogenic noise, low signal, and uncertainties in the inversion model likely reduced the comparative advantage that including AEM provided.AEM cannot supersede direct sampling where the model accuracy required exceed the resolution possible with the geophysical measurements. Nevertheless, with the algorithm we can identify high probability zones for shallow bedrock, identify steep or anomalous bedrock topography, and estimate the spatial variability of depth at earlier phases of investigation. Thus, we assert that our method is still useful where detailed mapping is the goal because it allows for more efficient planning of secondary phases of drilling.

Drilling Evolves as Exploration Campaign Moves to Deeper Water Offshore Mexico

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 25030, “Drilling Evolution of the Ultradeepwater Drilling Campaign in Mexico, Perdido Fold Belt,” by Victor G. Vallejo, Aciel Olivares, and Octavio Saavedra, Pemex, and Juan R. Lopez and Manuel E. Torres, Schlumberger, prepared for the 2014 Offshore Technology Conference Asia, Kuala Lumpur, 25–28.March. The paper has not been peer reviewed. During the 10-year period between 2003 and 2013, Mexico drilled 30 deep- and ultradeepwater wells in water depths ranging from 512 to 2900m. During this exploration period, the learning curve has improved with each subsequent level of difficulty and increased well depth. In order to reach water depths greater than 1500 m, both the wellbore geometry and the real-time data-acquisition strategy have changed. Introduction Fig. 1 shows how wellbore geometry evolved to reach geological targets and how the various hole diameters changed to meet exploration objectives. As seen on the left of the figure, a conventional drilling and data-acquisition approach was applied: drilling a 12¼-in. pilot hole for data acquisition and thereafter enlarging the hole to 17½ or 14¾ in. to set the casing. This enabled real-time logging-while-drilling (LWD) data acquisition and provided a 12¾-in. maximum hole size for wireline data acquisition. However, as water depth increased (right side of Fig. 1), the hole-size requirements for the mechanical well design increased accordingly. In some cases, with shallow geological targets, the required hole size of 22 in. was needed for the casing. This required a strategy to drill an appropriate hole size for LWD and wireline evaluation with minimal dedicated drilling and hole-enlargement trips. The evaluation programs considered realtime data needed to make decisions during the drilling phase and support decisions for a more- comprehensive wireline evaluation program if the zones warranted more extensive evaluation. The comprehensive evaluation logging suites included wireline-logging tools with triaxial resistivity, elemental-capture spectro scopy, nuclear magnetic resonance, vertical seismic profiles, mechanical sidewall coring, and the complete suite of formation-testing services for pressure and fluid sampling. The ultimate goal of the program was to provide accurate volumetrics, physical rock samples, and fluid samples for the booking of hydrocarbon reserves.

Managed-Pressure-Drilling Technology in Offshore HP/HT Gas/Condensate Fields

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 171429, ’The Deployment of Managed-Pressure-Drilling Technology To Assist in the Development of Offshore HP/HT Gas/Condensate Fields in Vietnam: Planning, Engineering, and Implementation,’ by Ben Gedge, Tan Chai Yong, Jordan Rao, Harpreet Kaur Dalgit Singh, Joseph Oracion, and Bao Ta Quoc, Weatherford; Nguyen Viet Bot, PVD Well Services; Nam Hong Tran, Tri Le Tran Minh, Richard Buitenhuis, and Lich Tran Dai, Bien Dong POC; and Alan E. Wittry, Peter Malpas, Aldric Beaugeois, Nhieu Nguyen Huu, and Nguyen Van Que, Cuu Long JOC, prepared for the 2014 SPE Asia Pacific Oil and Gas Conference and Exhibition, Adelaide, Australia, 14-16 October. The paper has not been peer reviewed. The paper discusses two gas/ condensate-development projects offshore Vietnam that deploy managed-pressure-drilling (MPD) technology. Bien Dong POC in 2010 commenced planning for the Bien Dong 1 high-pressure/high-temperature (HP/HT) gas/condensate-development project. The Bien Dong 1 development is a complex HP/HT project ranking as one of the most difficult and challenging projects of its kind in the Asia Pacific region. The second project covered by this paper is the gas-condensate development for Cuu Long JOC. Introduction The Bien Dong drilling team decided to deploy MPD technology in the planning phase of the development drilling and mobilized it for the first well drilled in the project. This decision was made because of the very low kick-and-loss margin and potential for ballooning and kick events, given the very high pore pressure. The frequency of well-control incidents can be higher in HP/HT wells; MPD enables easier control of kicks with the automated choke manifold. A semisubmersible tender assist rig is being used to drill all the current development wells; it is the largest of its type in the world and incorporates a quad mast. The MPD equipment was integrated into the rig on a flexible “plug-and- play” basis. The Cuu Long JOC wells, drilled from a cantilever jack-up over the platform, had somewhat different drivers, given that a number of wells in this field had previously encountered challenges that MPD could mitigate. These included low rates of penetration and fracture-induced losses because of the equivalent-circulating-density (ECD) effect. Managing the ECD became the main driver as experience was gained with MPD.

Technology Focus: Well Integrity (January 2015)

Technology Focus Cementing operations represent one of the more critical aspects concerning well integrity. Despite the large amount of research and the huge number of operations throughout the years, the industry still faces well-integrity problems during and after cementing operations. These occurrences have been experienced by the petroleum industry worldwide and can happen at any moment of the well life cycle, from the drilling phase to abandonment after the well’s production life. Here, I have categorized these well-integrity issues according to the moment at which they manifest: during the cement displacement inside the well (minutes); after the cement placement (hours to days), and after the cement has been cured (months to years). The first category may result in serious well-control problems, including blowouts (the Macondo blowout was related to cementing operations). According to a survey published by the former Minerals Management Service, during the period between 1992 and 2006, the leading factor contributing to blowouts in the US offshore area was cementing (18 out of 54 blowouts reported). These well-control problems are normally caused by improper design of the cementing operation in terms of hydrostatic pressure of the cement slurries or preflushes, failure when mixing the cement slurry to achieve its planned density, lost circulation during the cement displacement, or failure of casing float equipment. In my opinion, well-control courses must dedicate more time to discussing well-control problems during cementing operations. The second category encompasses those issues normally associated with the loss of hydrostatic pressure of the cement slurry during its initial hydration period and consequent gas flow inside the annulus. This condition also can cause well-control problems, pressure buildup in the annulus between casing strings, and zonal-isolation problems later on. The industry has several ways to mitigate these occurrences that include, but are not limited to, the use of gas-block additives, the design of cement slurries with short transition times, the application of surface pressure on the annulus, the use of external casing packers, and the implementation of multistage cementing operations. Despite the application of these mitigation measures, annular gas flow after cementing is still a recurrent problem, and remedial solutions are normally expensive and difficult. The last category refers to long-term problems normally caused by poor cementing practices, with detrimental effects on zonal isolation. Inadequate drilling-mud removal during the cement-slurry displacement in the annulus, insufficient cement height that may lead to casing leakage and corrosion problems, and the channels that result from the gas flow previously mentioned are some of the factors that can contribute to long-term well-integrity failures. Again, remedial solutions are normally expensive. JPT Recommended additional reading at OnePetro: www.onepetro.org. IPTC 16592 Mitigation of Deepwater Shallow Hazards With Simplified Cement System: South China Sea Case Study by Todd B. Ellis, Baker Hughes, et al. OTC 24369 Well-Integrity Analysis Applied to Workover Prediction by T.C. da Fonseca, Petrobras, et al. SPE/IADC 163474 Automated Alarms for Smart Flowback Fingerprinting and Early Kick Detection by Tarab H. Ali, Baker Hughes, et al.

Technology Focus: Wellbore Tubulars (June 2014)

Technology Focus NORSOK (the competitive standing of the Norwegian sector), as most know, is the industry initiative to add value, reduce cost and lead time, and eliminate unnecessary activities in offshore field developments and operations. The NORSOK-010 Rev. 4 Standard document defines requirements and guidelines regarding well integrity in drilling and well activities. It defines well integrity as the “application of technical, operational, and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well.” The NORSOK standard focuses on establishing well barriers by use of well-barrier elements in conjunction with their acceptance criteria, their use, and monitoring of integrity during their life cycle. Further, it defines a well-barrier element as a physical element that in itself does not prevent flow but, in combination with other well-barrier elements, forms a well barrier. The standard focuses strongly on the establishment of well barriers and well-barrier elements and on how these are accepted and monitored to prevent loss of well integrity that ultimately could lead to a loss in wellbore-fluid containment. The general principle of the two-barrier concept is that two well barriers should be in place at all times to ensure the provision of well integrity. In the drilling phase, the primary well barrier is typically the fluid column. Secondary well-barrier elements can be the in-situ formation, casing cement, casing, wellhead, high-pressure riser, or drilling blowout preventer.