bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyethylene Glycol PEG Functionalized Silane for Highly Efficient Silicate Scale Control
Authors: Meng Fei , Aften Carl
Published: March 2017

Sandstone reservoirs flooded with alkaline surfactant polymer (ASP) are associated with silicate scaling of production wells. Silicate scaling has been a significant problem in ASP-flooded areas in China and Canada. This paper reports a series of highly effective silicate scale inhibitors comprised of polyethylene-glycol-functionalized silane.

Surface chemistry of silicate was utilized to prevent scale growth. Silane/siloxide groups bond well with the surface of silica and silicates. The introduction of a silane/siloxide group into a scale inhibitor can greatly enhance the affinity of inhibitor molecules with the silicate surface. Conversely a silicate surface also has exposed OH groups which can form hydrogen bonds with the oxygen atoms in the backbone of PEG. The PEG polymer chain is likely to wrap around the surface of silicate nuclei, thus becoming a blocking layer and inhibiting further silicate growth.

Both static and dynamic tests were utilized to evaluate the performance of the silicate scale inhibitors. The PEG-functionalized silane achieved excellent inhibition percentages at low or medium pH as compared with conventional inhibitors that are based on phosphonates or polycarboxylic acids. When brine solution pH is high, magnesium (Mg) and calcium (Ca) silicate form, grow larger, and precipitate out, before effective inhibition can occur. This research found the addition of Mg/Ca sequesters help mitigate this growth/precipitation problem by slowing the initial nucleation process.

This novel study supports the introduction of a silane/siloxide group that specifically binds the inhibitor with silicate nuclei providing the advantages over conventional technologies where no specific binding between an inhibitor and precipitate is established.
Characterization of Filter Cake Generated by Nanoparticle-Based Drilling Fluid for HP/HT Applications
Authors: Mahmoud Omar , Nasr-El-Din Hisham A. , Vryzas Zisis , Kelessidis Vassilios C.
Published: March 2017

As high-pressure/high-temperature (HP/HT) drilling is inherently expensive, drilling fluids and technologies should be carefully selected to successfully handle the associated challenges. Over the past few years, nanoparticles (NPs), among other additives, have been investigated to address these challenges. The objective of this study is to investigate the potential of using ferric oxide NPs on the filter cake properties in downhle drilling environments.

Having an efficient filter cake is an important property of the drilling fluid and can affect the success of drilling operations. This research focuses oncharacterizatingthe filter cakes produced by Ca-bentonite-based drilling fluid contains ferric oxide NPs at downhle conditions. A combination of computed-tomography (CT) scan and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used in filter cake characterization. The effect of NP concentration, fluid preparation method, and filtration condition were studied. A HP/HT filter press was used to perform the filtration process at conditions up to 350°F and 500 psi. Indiana limestone core disks were used to simulate the filter media.

The experimental results showed that the ferric oxide NPs improve the filter cake and filtration properties of Ca-bentonite-based drilling fluid in the presence of polymer and other additives. Low NP concentration is preferred for obtaining a good cake quality with the best characteristics obtained at 0.3–0.5 wt% NPs. Furthermore, this drilling fluid can withstand conditions up to 500 psi and 350°F. Cake properties of 0.151 in. thickness, 6.9 ml filtrate volume, and 0.428 µd permeability was obtained at such conditions. The addition of NPs to the drilling fluid improved the filter cake properties under both static and dynamic filtration. SEM-EDS analysis confirmed the efficiency of using NPs to form a smoother/less porous filter cake morphology. Moreover, sonication for one hour and hydration for 16 hours are recommendedfor better preparation of these fluids.

This research provides an experimental evaluation of using ferric oxide NPs with Ca-bentonite-based drilling fluid to produce high-quality filter cake at downhole conditions. The characteristics of the filter cake gererated confirmed the efficiency of such fluids.
Hydrophobically Associating Polymer Water-in-Oil Emulsions Used in Multi-pad Fracking for Tight Oil Reservoir: The First Example in China
Authors: Lv Yongli , Feng Yujun , Wang Zenglin , Li Aishan , Zhang Quansheng , Huang Bo , Zuo Jiaqiang , Ren Zhanchun , Chen Yong
Published: March 2017

Multi-pad hydraulic fracturing is believed a cost-effective procedure to unlock the tight oil from low-porosity, low-permeability reservoirs. However, the inconvenience of difficult-dissolving process at surface and crosslinking of the conventional guar-based fracturing fluid systems cannot satisfy such fracking jobs because of the massive proppant loading, high flow rate and large volume of the fluids used.

To address these issues, a crosslinking-free and rapid-dissolution fracturing fluid system based on synthetic hydrophobically associating polymer (HAP) "water-in-oil" emulsion was developed. The HAPs are derived from classical water-soluble polymers by incorporating small amount of long hydrophobic side chains onto the polymer backbone. When above a critical associating concentration, these polymers can automatically form a three-dimensional transient network by intermolecular association, reminiscent of cross-linked structures, offering the suspending capacity for proppants. With inverse emulsion polymerization, the obtained HAP emulsions can not only get high molecular weight, but also be rapidly dispersed and finally dissolved within 5 minutes.

It was found concentrated HAP polymer emulsions can be dispersed online with surface water or even produced fluids to get final designed concentration. Laboratory rheological study shows that 1% of the as-prepared fracturing fluid can reach more than 50 mPa%s at 150 0C. Compared with guar-based fluid, the HAP fracturing fluid can be completely broken, and the viscosity, surface tension, skin damage of the residual fluid on the permeability are all smaller, while the fluid loss is comparable, proppant-carrying ability is even better. Most importantly, no further surfactant was needed to assist the flowback the fluid.

Since September 2013, such associative polymer fracturing fluids were successively used in 29 wells of 3 well pads, Yan-227, Yan-22 and Bin-37 blocks in Shengli Oilfield, Sinopec, where the temperature ranges from 110 to 145 cC. Totally 60,000 m3 fluids were consumed in these fracking jobs, and 87, 9, and 45 stages were successively fractured in the horizontal sections, respectively.
A New Application of Potassium Nitrate as an Environmentally Friendly Clay Stabilizer in Water-Based Drilling Fluids
Authors: Zhou J. , Nasr-El-Din H. A.
Published: March 2017

Currently, the application of potassium chloride (KCl) as a temporary clay stabilizing additive in water-based drilling fluids is challenging in chloride-sensitive formations due to problems with wellbore stability and drilling fluid. Its use can also impose significant additional costs to drilling operations. In addition, the chloride ions can cause contamination, with the potential to inhibit the growth of vegetation and to pollute aquifers. The purpose of this study is to propose a new high-performance water-based fluid system using potassium nitrate (KNO3) instead of potassium chloride as a clay-stabilizing additive for drilling applications.

Water-based drilling fluids using potassium nitrate and potassium chloride, respectively, were prepared with a density of 1.3 S.G. using API barite (BaSO4, D50=15-20 μm, S.G.=4.2), manganese tetraoxide (Mn3O4, D50=1 μm, S.G.=4.8), or micronized ilmenite (FeTiO3, D50=5 μm, S.G.=4.5-4.7) as weighting materials. The Capillary Suction Time (CST) test was used to optimize the brine concentration in drilling fluids for effective clay swelling inhibition. High-pressure/high-temperature (HP/HT) filtration tests were conducted under static conditions at 250°F and 300 psi. Berea sandstone cores with an average porosity of 23 vol% and an average permeability of 100 md were used in the filtration tests. The rheological properties, the volume of filtrate and the filter cake thickness generated by the water-based drilling fluids were determined and compared.

CST results show that potassium nitrate exhibits characteristics similar to potassium chloride as a clay stabilizer above 4 wt% concentration. The water-based drilling fluid containing potassium nitrate has very similar rheological properties when compared with potassium chloride. The HP/HT filtration press results show that water-based drilling fluid with potassium nitrate has a low filtration volume, less than 1 cm3, and formed thinner filter cake when using API barite as the weighting material. This paper not only highlights the successful replacement of KCl by KNO3 to achieve good rheological properties in water-based drilling fluids, but also shows that KNO3-based drilling fluids are more environmentally friendly than KCl-based drilling fluids.
Effective Removal of Hydrogen Sulfide and Mercaptans in Oilfield Applications
Authors: Chakraborty Soma , Lehrer Scott , Ramachandran Sunder
Published: March 2017

Sulfur contaminants in the form of hydrogen sulfide and mercaptans are undesirable for various reasons during sour crude production. For example, hydrogen sulfide and mercaptans can be hazardous to personnel. Their presence can create major corrosion issues pertaining to the assets. Furthermore, these components can be objectionable because of their chemical reaction with other hydrocarbons or fuel system components. In addition to the risk of direct harm to exposed personnel, products and equipment, environmental considerations such as odor and emission control must also be addressed. Increasing urbanization is moving more and more housing developments within the affected zone of many facilities. Depending on local and national regulations, penalties and fines can result from exceeding either hydrogen sulfide or mercaptan emissions standards.

There are several chemistries available for treating hydrocarbon feeds containing sulfur compounds and acidic components like hydrogen sulfide and mercaptans. The early processes included treatment of the hydrocarbon fractions with caustic, clays and hydro-treating as well as the UOP Merox™ process. One disadvantage of caustic treatment is that disposal of spent caustic is undesirable for environmental reasons. One of the most popular methods of treatment comprises scrubbing with mono or diethanolamine in a regenerative amine system. Amine systems, however, cannot sufficiently remove mercaptans. Although several chemistries are effective in scavenging hydrogen sulfide, there is a need for chemistries effective for scavenging mercaptans, especially in the presence of hydrogen sulfide.

The paper presents new chemistries that scavenge hydrogen sulfide and simultaneously scavange mercaptans extremely efficiently. A lab technique is also presented that was designed to mimic a field gas-tower application. A new analytical technique is described that simultaneously detects hydrogen sulfide and mercaptans. The gas concentrations are detected before and after scavenging. A systematic performance evaluation proves the efficacy of the scavengers in simultaneously scavenging hydrogen sulfide as well as mercaptans.
Fast and Accurate Screening and Evaluation of Halite Scale Inhibitors by Two Novel Static Bottle Testing Methods
Authors: Ruan Gedeng , Kan Amy T. , Dai Zhaoyi , Yan Fei , Zhang Fangfu , Bhandari Narayan , Alsaiari Hamad A. , Liu Ya , Zhang Zhang , Lu Yi-Tsung , Deng Guannan , Tomson Mason B.
Published: March 2017

Halite (NaCl) scale is a non-conventional scale, which happens due to the temperature or pressure drop, or water evaporation at extremely high TDS environment (TDS up to 350,000 mg/L), such as deepwater field, shale formations, gas and gas condenstate fields. Compared to other conventional mineral scales, like barite or calcite, there is no standardized experimental procedure to screen and evaluate halite scale inhibitors. Because of the extremely high solubility of NaCl, it is very challenging but important to accurately control and calculate the halite saturation index (SI) or saturation ratio (SR) experimentally and theoretically. The Brine Chemistry Consortium has been continuously working on the development and optimization of the thermodynamic model, ScaleSoftPitzer (SSP), for the the prediction of the solubility and scaling risks of various minerals in mixed electrolytes over a wide range of temperature and pressure based on Pitzer theory. Recently the new SSP2017 version which can predict the halite SI within SI error of 0.01 from 25 to 90 °C with up to 1.0 m Ca2+ (~35,000 mg/L). In this study, two static bottle testing methods have been developed by taking the advantage of the powerful calculation ability of SSP2017 to fast and accurately screen and evaluate the inhibition efficiency of different chemicals. The Method One is a temperature-driven and monitoring method and the Method Two is a brine-mixing method of mixing a naturally saturated NaCl solution, a highly concentrated chloride salt solution and an inhibitor solution. By using these two novel methods, over 40 different chemicals are screened and evaluated, including small molecules and polymers in the category of polyacrylate, polyaspartate, polysulfonate, carboxylate sulfonate copolymer, phosphonate polymer, etc. From the experimental results, five carboxylate sulfonate copolymers (Inh #H14, #H23, #H26, #H30, #H40) have better inhibition efficiency. The synergistic effect of Inh #H40 and Fe(CN)64– is also investigated, and 130 mg/L of Inh #H40 and 20 mg/L of Fe(CN)64– can effectively inhibit the halite scale at simulated field condition of SI = 0.09 (SR = 1.23, TDS ~ 353,800 mg/L) and 0.6 m Ca2+ at 70 °C. In summary, two fast and accurate methods have been developed for the screening and evaluation of halite scale inhibitors, and with the usage of effective halite scale inhibitors, the costs of halite scale control can be significantly reduced both in freshwater usage for dilution and high-salinity produced water treatment.
Micro-Sonde Well Logging System
Authors: Gardner D. , Hjelstuen M. , Fallet T. R. , Fallet Truls , Kragset S. , Lohne H. P. , Husby K. , Hamou F. R. , Stamnes Ø. , Belle B.
Published: March 2017

The micro-sonde well logging system utilizes miniaturized data logging devices, which are released at the bottom of a well and record downhole parameters whilst being transported by fluid flow to surface.

The μSonde capsules are designed to be small enough to pass restrictions without obstructing the flow path. Each sonde is activated when launched and thereafter records sensor measurements to a memory. Typical measurements include pressure, temperature, motion and fluid electrical properties. Upon reaching surface, wireless communication transfers the recorded data for analysis.

For production wells a magazine carrying μSondes is deployed to the bottom of the well and thereafter, based on predetermined well conditions and/or time intervals, the sondes are released. For drilling operations, the μSonde storage magazine is deployed together with the bottom hole assembly. The sondes are constructed from low density materials such that their effective density can be matched to the well fluid.

Applications and design requirements for the μSonde well logging system have been investigated for drilling operations and production well surveys.

The development of the micro-sonde (μSonde) well logging system is supported by the Research Council of Norway' Petromaks 2 Ground breaking technology research program.
The CHAOS-X Model and Uncertainty Values for Magnetic Directional Surveying
Authors: Herland E. V. , Finlay C. C. , Olsen N. , Edvardsen I. , Nordgård-Hansen E. , Laundal K. M. , Waag T. I.
Published: March 2017

The Earth's magnetic field provides a unique natural source of orientation information that is particularly useful for subsurface magnetic measurement-while-drilling (MWD) navigation. In order to utilize the MWD magnetic field measurements for calculating the orientation of the bottom hole assembly (BHA), an accurate geomagnetic reference model is needed for comparison. In this paper we present the CHAOS-X model, a new geomagnetic reference model that provides global vector field estimates of Earth's magnetic field, with high resolution in both space and time, for precision magnetic directional surveying applications.

The model is derived from more than one million satellite and ground-based observatory magnetic measurements and consists of modules representing internal sources (in the Earth's core and crust), mag-netospheric sources, and ionospheric sources. Compared with previous reference models, the CHAOS-X model is particularly designed for better characterization of the time variations in the geomagnetic field. In this paper, we describe the model and present benchmark comparisons with magnetic observatory data to establish the uncertainty values required in models of wellbore positional errors in magnetic directional surveying applications.

The discrepancy between geomagnetic measurements and reference models are typically dominated by spatial variations caused by local geology. In applications requiring high accuracy, these variations can be taken into account by using a dedicated local model. In such cases, when the errors associated with local geology is small, our results show that the CHAOS-X reference model may yield a significant improvement compared with existing reference models. This result holds both when the model is used predictively and retrospectively. We also argue that using a model with an accurate description of the time variations improves recent magnetic surveys while drilling, since the description of the rapid time variations can be updated near real-time.
Pneumatic Conveying of Model Drill Cuttings - Pilot Scale Experiments and Simulations
Authors: Malagalage A. , Ratnayake C. , Ariyaratne W. K. , Melaaen Morten C. , Aas Nina
Published: March 2017

The offshore drilling operations generate huge volume of drill cuttings. Rig site transfer of cuttings can be a challenge both if pneumatic conveyors or screw conveyors are used. Especially, wet powder is a challenge since the particles become too sticky for easy handling or too dry for acting like a slurry. This paper presents the preliminary results of a scientific investigation aimed to study transport properties and storage criterion of dry and partially-moist solids drill cuttings. Model materials have been tested in pilot scale pneumatic conveying rigs and CFD simulation on particle conveying has been performed in parallel. The pilot scale tests have been conducted for the sand particles in the size range of 0.1 – 3 mm diameter under the air flow rate of 13-23 ms-1 The simulations were carried out using multiphase particle-in-cell method (MP-PIC) for dry particles that are having particle size distribution in the range of 0.3-3 mm diameter. Pressure drop in a horizontal section is studied and it was observed that at a minimum pressure drop and a minimum specific power requirement is reached when decreasing the superficial air velocity. This region can be considered as the economical region for operation. For the considerd particle size this region was obtained at the air velocity of 16-19 ms-1 for a horizontal pipe section with 81.2 mm diameter.

In the simulations, the predicted pressure drops in 15-22 ms-1 velocity range are in good agreement with experimental results. The combination of pilot scale pneumatic conveying tests and simulations of dry drill cuttings provide a platform to evaluate and predict pneumatic conveying parameters for partially-moist drill cuttings.
Extended-Reach Open-Hole Gravel Pack Completion under Multiple Complexities
Authors: Aggarwal Vishal , Gupta Vaibhav , Narayan Shashank , Horatio-da-Costa Shado Olushola
Published: March 2017

This paper aims to discuss completion of deepwater open-hole gas wells that were completed using an alternate paths system (APS) and a state-of-the-art viscoelastic surfactant (VES) carrier fluid. The wells presented multiple design and operational complexities such as high bottomhole temperature, narrow fracturing window, extended horizontal laterals, and unstable shale zones. Operational and design steps considered to overcome these complexities are discussed, making this literature a resource that maps obstacles and presents viable solutions faced in any similar operation. These complexities combined with deepwater operational requirementsand economics made cost of failure unacceptable.

Two 8.5-in. openhole depleted gas wells upto bottomhole temperature of 230 °F were completed with gravel pack treatments using a VES carrier fluid to counter sand settling, minimize friction pressures, and optimize fluid viscosity. The operations pumped 200% excess proppant compared to design volume to ensure complete packs downhole, countering any thief zones or open-hole washout regions. Returns were taken through the BOPvia mud line to avoiding high fluid friction in the choke line. In one case, the riser was displaced with lighter base oil to reduce the bottomhole pressures.

Using the alternate path system and VES carrier fluid proved to be highly successful in these wells, as compared to the pre-drilled liners and standalone screens used previously in the same field. Complete packswere obtained within narrow fracture gradient windows inall cases. After reversing out the slurry, a filter cake dissolver treatment was also performed to decrease the flow initiation pressure for the well. Case studies have been presented elaborating completions plan and execution of open hole gravel pack treatment for two 8.5-in wells.

This literature is a case study elaborating operational procedures that have proved to be successful in performing open-hole gravel packs under complex constraints. This paper serves as a reference, highlighting obstacles faced and presenting viable solutions for any similar operation.
Comparing Reservoir Fluid Models to PVT Laboratory Measurements
Authors: Meisingset Knut Kristian , Yang Tao
Published: March 2017

To prove that PVT input to reservoir models is representative, the comparison between the modeling of PVT data and relevant PVT laboratory measurements should preferably be as direct as possible.

A black oil reservoir simulation model can be described as a compositional model with only two hydrocarbon components (‘oil’ and ‘gas’). The reservoir fluid is represented by a set of tables, defining oil and gas viscosity and formation volume factor as a function of pressure, temperature and composition.

Examples on quality assurance of fluid modeling by direct comparison of PVT input for black oil and compositional reservoir simulation with PVT laboratory measurements are shown in the present paper, including results from Differential Gas Liberation (DGL) for reservoir oil and Constant Volume Depletion (CVD) for reservoir gas.

Challenges with regard to black-oil modeling of depth gradients are also discussed.
Sustained Intervention Campaigns Over a 10-Year Period with Riserless Light Well Intervention Vessels Enables North Sea Operator to Improve Operational Efficiency and Increase Recovery from its Subsea Fields
Authors: Varne T. , Jorgensen E. , Gjertsen J. , Osugo L. , Friedberg R. , Halvorsen E. C.
Published: March 2017

This paper describes the approach, experience and results achieved by a North Sea operator (the Operator) when using purpose-built riserless light well intervention (RLWI) vessels to perform continuous well intervention operations on its subsea fields over the last 10 years. Using RLWI vessels on a continuous basis, the Operator has been able to; achieve a high intervention intensity on its subsea wells (345% increase—from 11 wells in 2006 to 49 wells in 2016), lower the intervention cost per well and improve field recovery factors. The contributory factors to these successes that are covered in this paper are: –Continuous improvements in efficiency during all stages of the intervention operation. This has resulted in the capacity to perform more interventions and hence a lower intervention cost per well. Specifically, over the last 10 years, there has been a 60% decrease in the average number of days to perform an operation.–Improved reservoir management, as a result of regular data acquisition of production and saturation monitoring logs.–Introduction of new technologies and the improved robustness of powered mechanical intervention systems. This has enabled more complex intervention work scopes, such as milling and manipulation of completion components, which would previously have required a modular offshore drilling unit (MODU).

The next target, is to reach water depths deeper than 1500 m. Some of the main challenges and equipment upgrades required to work at these depths are discussed.
A Novel Approach to New Field Development - Application of Reservoir Mapping Technology to the Ivar Aasen Field Development for Maximizing Field Performance and Improving Reservoir Characterization
Authors: Jøssund Tor-Ole , Elfenbein Carsten , Johansen Yngve Bolstad , Drange Ingrid Sætre , Olsborg Lodve Hugo , Skorve Torstein , Kvilaas Geir-Frode , Christoffersen Kjell , Mastad Sigbjørn , Stubsjøen Marte , Wang Haifeng , Denichou Jean-Michel , Charef-Khodja Hakima
Published: March 2017

The Ivar Aasen field was discovered in 2008 and consists of two main groups of reservoirs – the Jurassic and Triassic reservoir zones. The reservoir architecture is complicated by their different depositional settings and by syn- and post-sedimentary faulting. Developing a new field of such complexity is a challenging task that demands a novel approach to optimize well placement and improve reservoir characterization.

Reservoir mapping while drilling (RMWD) technology has recently been introduced to the industry, providing an array of deep, directional measurements that are converted to a resistivity map of the formation out to approximately 30 m above and below the borehole. The reservoir mapping results are available for the operator to make geosteering decisions during drilling, to optimize the completion design with inflow control devices after TD, and to update the post-well reservoir model for planning the next wells. This process helps the operator maximize the benefits from the already drilled well on the yet-to-drill wells. The sequence of the wells to be drilled can be logically arranged to leverage the maximum value from the information that reservoir mapping provides.

The drilling campaign on the Ivar Aasen field started in summer 2015 and the RMWD technology was used while drilling all the production wells. It revealed that the actual reservoir structure was even more complex than originally expected, and enabled the operator to pursue the best well path to maximize field production potential. This was achieved by using the data to actively geosteer, estimate reservoir producibility (through permeability-thickness calculation) in real-time to decide on TD, and by sidetracking to new targets revealed by the mapping. This new approach can also be applied to infill campaigns on existing fields. In this paper, one of the producer wells are reviewed in details to illustrate the process and demonstrate the results.
Drilling Fluid Rheology Under High Pressure High Temperature Conditions and its Impact on the Rate of Penetration
Authors: Sukhoboka Olha
Published: March 2017

The aim of this paper is to investigate the temperature and pressure dependent rheology of drilling fluids, and show its effect on the rate of penetration. A better understanding of the mechanisms that affect the rate of penetration is necessary because the high costs of the high pressure high temperature wells often make the field development economically inefficient.

To achieve the goal of the study, laboratory experiments on temperature and pressure dependent rheology of various drilling fluid samples were conducted. The experiments show that temperature has a more significant effect on the drilling fluid viscosity than pressure. In addition, computer modelling of the rate of penetation was done. As a result of the modelling, it was observed that the temperature does not have a significant effect on the rate of penetration.
Influence of Construction and Deterioration on Platform Well Life Extension
Authors: Saleh Hassan , Rimmer Alex
Published: March 2017

One of the most common challenges faced by well operators worldwide is extending the lifetime of their aging platform wells. The initial well construction, operational loading and time-dependent deterioration of a well through field life are all key factors that need to be understood to establish the remaining capacity of a well. However, often these factors are not fully understood and consequently costly decisions to repair or abandon wells can be made unnecessarily, or in some cases critical wells or operations on wells are not identified, risking structural collapse of a well. To address these issues, this paper describes the factors that influence the integrity of the well, and presents advances in the approaches to understand and evaluate the condition of a well and hence better evaluate remaining capacity. Methods, Procedures, Process: Typically, corrosion of the casings is taken as the key parameter to establish a well's remaining capacity. However, as demonstrated in this paper through an analytical evaluation, the axial loading in the well is another key parameter that needs to be understood. A range of factors affect the well axial loads based on well construction and deterioration is considered, including: Weight of casing hung off wellhead during installationLevel of axial support provided by casing shoeCement levelsChanges to well configurationChanges to well service (Producer to Injector)Changes to operating temperatures and pressures through field lifeCorrosion and other deterioration of the conductor and casings

This information can, however, be difficult to obtain due to incomplete or inaccurate construction records or difficulties in taking direct measurements or inspecting a well. This paper demonstrates the influence of each of these variables on the capacity of the well, how the uncertainty in these variables affects this assessment, and consequently the overall uncertainties in establishing the remaining capacity of a well. Results, Observations, Conclusions: Having established the limitations and uncertainties of an analytical evaluation and the need to establish well axial loads, the paper also proposes a method to characterise the axial loads in a well, including a proposed technique for in-field measurement as an input to establishing a well's on going fitness for service alongside corrosion measurements. Novel/Additive Information: Overall, the paper presents an improved approach to establishing the suitability of a well for life extension based on an improved understanding of the influence of well loads, with widespread application to aging platforms in the North Sea and globally.
Multilevel Force-Balanced Cutting Structure Layout Helped Solve PDC Bit Dullness Issues Resulting from Geosteering in Thin Reservoirs
Authors: El-Gayar Mahmoud , Ali Tarek Samy , Talaf Mansour Abu
Published: March 2017

Thin reservoirs of a few feet in thickness present challenges to well placement. The challenges generally involve remaining within the reservoir boundaries and undergoing as few exits as possible. Geosteering is typically used to optimize wellbore placement in the productive reservoir to maximize hydrocarbon production. The challenge posed by the subject reservoir in this study was a combination of the thinness of the reservoir and the highly resistive environments of the boundary, including formation heterogeneity and low porosity anhydrite formations.

Steering in this challenging environment using a rotary steerable system (RSS) resulted in premature cutting structure damage of the polycrystalline diamond compact (PDC) bits. This damage led to a significant increase in nonproductive time (NPT) resulting from tripping out of the hole for bit changes. A customized PDC bit design was necessary for the drilling operation to address the dull conditions, maintain a competitive rate of penetration (ROP), provide smooth borehole quality, and maintain low vibration levels. A new PDC bit was designed using patented multilevel force balancing technology: a new theory of PDC cutter layout in force-balanced groups. By carefully selecting the order of cutter layout groups, an even distribution of the cutting structure forces was obtained, thus reducing the imbalance forces induced as the bit entered transit lithologies.

This PDC bit design and the implementation of the integrated engineering software used to analyze offset well data, drilling parameters, bit walk tendency, and rock mechanics significantly affected the horizontal section drilling performance. A single new bit design was used to drill three laterals from shoe to total depth (TD) while achieving a new field ROP record. The bit was pulled out of hole (POOH) twice in green dull condition. The successful implementation of the multilevel force-balancing technology improved overall bit stability, reduced vibration levels, and increased the horizontal section drilling efficiency.

This paper demonstrates the successful implementation of an innovative PDC cutting structure layout using computer-aided design (CAD) and computer-aided manufacturing (CAM) software for bit design and optimization. The PDC bit design software incorporates a steering mechanism, bit/formation interaction model, and advanced rock mechanics modeling software to help predict bottomhole drilling mechanics, thus helping to create an optimized engineering solution for enhanced drilling efficiency.
Drilling an ERD Well on the Statfjord Field, North Sea
Authors: Hussain Sajjad , Dhaher Karam Sulaiman , Bjoerneli Hans Magnus , Blackburn Jason , Monterrosa Leida , Jakobsen Tom , Otto Monsen Gisle , Haaland Sigurd , Dahl Johan , Østensen Ståle , Fjelde Kjell Kåre
Published: March 2017

Old platforms are not well known for extended-reach drilling (ERD) operations mainly due to rig and hydraulics limitations. ERD wells demand robust rig capabilities, good hydraulics systems, and equipment reliability. In addition, the well profile, rotary steerable system (RSS), measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools, surveying, and new technologies are extremely important to the success in drilling an ERD well. RSS and drillpipe selection are important factors for hydraulics optimization. Surveying techniques are also important for time saving and improved efficiency. An ERD well in the North Sea Statfjord field was kicked off in the 17 ½-in. section from the openhole cement plug through a 50-m window between the 20-in. casing shoe and 13 3/8-in. casing stump, ensuring a smooth well profile and reduced doglegs compared to the whipstock window exit. The 17 ½-in. section was drilled and landed at a 79° inclination using point-the-bit RSS technology, and the 12 ¼-in. section was drilled in two runs as planned using the point-the-bit RSS withstanding more than 550 h down hole. The 9 5/8-in. liner was run and floated successfully in the ~6000-m section. Strict adherence to surveying techniques and quality control processes proved very helpful to meet Operator technical requirements. The 8 ½-in. section was drilled and landed on top of the reservoir with an inclination decrease from 88° to 35°. New MWD technology was successfully used in drilling the 6-in. section. These latest technologies as well as employing appropriate techniques help to drill ERD wells on aged platforms like those in the Statfjord field. This paper will describe the planning and execution phases of a challenging ERD well drilled in the Statfjord field.
Data Driven Adaptive Localization With Applications To Ensemble-Based 4D Seismic History Matching
Authors: Luo Xiaodong , Bhakta Tuhin , Nædal Geir
Published: March 2017

Ensemble-based history matching methods have received great attention in reservoir engineering. In real applications, small ensembles are often used in reservoir simulations to reduce the computational costs. A small ensemble size may lead to ensemble collapse, a phenomenon in which the spread of the ensemble of history-matched reservoir models becomes extremely small. Ensemble collapse is not desired for an ensemble-based history matching method, because it will not only deteriorate the capacity in uncertainty quantification, but also force the ensemble-based method to stop updating reservoir models later on. In practice, distance-based localization is thus introduced to prevent ensemble collapse. Distance-based localization works well in many problems. However, one prerequisite in using distance-based localization is that the observations have associated physical locations. In certain circumstances with complex observations, this may not be true, and it thus becomes changeling to apply distance-based localization.

In this work, we propose a data driven adaptive localization scheme that does not reply on the physical locations of the observations. Instead, we use the spatial distributions of the correlations between model variables and the corresponding simulated observations. In the course of history matching, we update model variables by only using the observations that have relatively high correlations with them, while excluding those that have relatively low correlations.

We demonstrate the efficacy of the proposed localization scheme in one 2D and one 3D seismic history matching problems. In both problems, ensemble collapse is severe in the presence of large amounts of observational data, but distance-based localization is not applicable due to the lack of physical locations of the seismic data in use. In contrast, correlation-based localization not only works well to prevent ensemble collapse, and also renders good history matching results.
Perforate, Wash and Cement PWC Verification Process and an Industry Standard for Barrier Acceptance Criteria
Authors: Delabroy Laurent , Rodrigues David , Norum Espen , Straume Martin , Halvorsen Knut H.
Published: March 2017

When permanently abandoning a well, each seal above a Distinct Permeable Zone (DPZ) needs to be restored with a cross-sectional barrier that will withstand the test of time. The Perforate, Wash and Cement (PWC) technology was developed as an alternative to section milling in situations where the wellbore barrier needs to be placed across a section of uncemented casing. Section milling is time consuming and results in exposing the BOP to swarf. The PWC method, on the other hand, is a more time-efficient process that consists of perforating the casing, washing the annulus behind it, and placing cement across the whole cross-section of the wellbore in a single run. However, some of the efficiency gain of the PWC method over section milling is lost when it comes to the barrier verification process. For section milled plugs, the verification process is usually the same as the one used for conventional wellbore cement plugs, since all the casing has been removed across the section milled window: the plug needs to be tagged/weight tested and pressure tested (except for section milled plugs where the top of the plug is left in open hole). On the other hand, as over 90% of the casing remains when installing a cross sectional barrier with PWC, the verification process typically involves two steps: 1) verify the annular component of the barrier, and 2) verify its internal one. In order to verify the annular part of the barrier, the internal barrier (cement plug) needs to be drilled out, and the annulus logged with a cement bond logging tool. A new internal cement plug then needs to be re-set and verified using the same verification method as for section milled plugs.

During the first phase of the Valhall DP Plug & Abandonment (P&A) campaign, the PWC technique was used repeatedly to create primary and secondary barriers in the 9 5/8″ casing and 9 5/8″ casing × 12 1/4″ hole annulus, each time using the same design and execution parameters. After building a successful track record of PWC jobs in 9 5/8″ casing, a process was initiated to develop a non-destructive and more efficient alternative verification process, specific to PWC operations that would not require to systematically having to drill out the wellbore cement to log the annular barrier. The intention was to base this alternative verification method on a consistent track record, a strict design and operational parameter set (Qualification Matrix), and to include this alternative verification method in a proposed NORSOK Element Acceptance Criteria (EAC) Table specific to barriers installed using the PWC technique. This PWC EAC Table is intended to be used as a best practice for designing, executing and verifying PWC jobs, and is recommended for implementation into the next revision of the NORSOK D-010 Guideline.
Ditch Magnet Removal of Steel Particles
Authors: Pattarini Giorgio , Strømø Kjartan Moe , Saasen Arild , Amundsen Per Amund , Pallin Jan Egil , Hodne Helge
Published: March 2017

Drilling fluids contain magnetic contaminations that negatively affect Measurement While Drilling directional tools and causes damage to the equipment in contact with the fluid. The effect is relevant while drilling long deviated wells. Ditch magnets are routinely installed in the fluid system to remove magnetic particles while drilling, with the purpose of protecting the Shale Shaker screens from large metallic debris, serve as monitoring tool to detect troubles in the drilling operations and clean the fluid from magnetic particles.

In this paper we describe field data for the operation and efficiency of the ditch magnets. An extensive set of samples of drilling fluid and of ditch magnets debris have been taken during offshore operations and have been brought onshore for detailed investigations. The material extracted has been assessed as constituted mainly by steel swarfs and steel fines.

The magnetic materials still present in the used drilling fluid have been extracted and quantified by a novel method that provide higher extraction rates and better accuracy than the methods currently employed in the industry, allowing to assess the actual content of magnetic contaminant. The magnetic susceptibility of the fluid has been measured and compared with values predicted for a known concentration of magnetic contaminants, allowing for the evaluation of the bias induced by them on the magnetometers of the MWD tools employed.

The capability of ditch magnets to remove the magnetic contaminants from fluid is quantified and compared with other available methods, like gravity separation, with special focus on the removal of magnetic particles in the range of few microns. Operational details and current issues in the deployment of ditch magnets are reviewed, and the most viable directions for improvement are briefly discussed.
Using Dual Desander and Stackable Filter Unit for Cleanout after Concentric Coiled Tubing Operation
Authors: Arefjord Anders , Malinauskaite Giedre
Published: March 2017

A well was completed in April 2014 and put online a day after completion. However, it was shut-in shortly after due to a production trip. Massive sand production (2 000 pounds per thousand barrels) was observed during the restart of the well. Sand free production could not be achieved by performing multiple choke reductions. The sand shut-off intervention failed and distributed acoustic sensing indicated multiple sand entry points along the wellbore.

A concentric coiled tubing (CCT) sand vacuuming operation was planned to be performed in order to clean out the well and reinstate production. A previously used conventional sand cyclone, and flowback system for CCT cleanout operations, needed to be replaced. This large unit had low separation efficiency resulting in excessive amounts of solids being transported to the process facilities. For a higher separation efficiency, this original unit was replaced by a compact (200cm x 200cm footprint) patented dual vessel desander, a passive design with no internal motor, and a stackable filter unit.

The system was first put into operation during a CCT sand vacuuming intervention to reinstate the production from the well. The use of the system resulted in major cost savings due to the introduction of a less complex surface solids removal system, and majorly reduced footprint, giving a reduced rig up/rig down time and improved HSE. In addition, the system resulted in increased operational efficiency due to the 100% removal of solids from the flow stream.

This paper describes a CCT sand cleanout operation where a dual vessel non-motorized desander, with a stackable filter unit, was used and discusses a case study presenting operational considerations, system description and results of the operation.
New Tubular Design Ellipse With Backup Pressure
Authors: Goodman Malcolm A. , Kalil Issa A. , McSpadden Albert R. , Coker Oliver D.
Published: March 2017

This paper develops a new von Mises ellipse based on backup pressure (internal pressure for collapse and external pressure for burst), so the new API collapse equations with dependence on internal pressure can be shown simultaneously on the same plot with the ellipse. Unlike the current ellipse used for casing and tubing design which is approximate, the new ellipse is exact for collapse, burst, and axial loads. Without the new ellipse, the approximate ellipse will continue to be used, and the new API collapse equations must be plotted separately. Example cases demonstrate the advantages of the new ellipse, including increased accuracy. Results help clarify many questions about the new API collapse equations, namely where they come from and how to use them.
Nitrogen Fertilizer Application Effects on Switchgrass Herbage Mass, Nutritive Value and Nutrient Removal
Authors: Obour Augustine K. , Harmoney Keith , Holman Johnathon D.
Published: March 2017

Switchgrass(Panicum virgatumL.) can provide summer forage when forage production from cool‐season grasses is limited. This experiment was conducted over two growing seasons (2014 and 2015) to determine nitrogen (N) fertilizer application rate and time of harvest effect on switchgrass herbage mass, nutritive value, and nutrient removal. Treatments consisted of a split‐plot arrangement of five N rates (0, 45, 80, 135, and 180 kg ha−1) applied annually as main plots and harvest time (harvested in July for forage or October for biomass) as subplots in a randomized complete block design with three replications. Nitrogen rate × time of harvest interaction had no effect on herbage mass or nutritive value. Increasing N application rates increased herbage mass, crude protein, in vitro dry matter digestibility, and neutral detergent fiber concentrations, but not acid detergent fiber. A quadratic function described the relationship between herbage mass and N rate, with maximum yield occurring at 151 kg N ha−1. The economic optimum N rates ranged from 90 to 120 kg N ha−1and depend on switchgrass hay price and N fertilizer costs. Generally, herbage mass was greater for switchgrass harvested for biomass, but nutritive value and nutrient removal were greater when switchgrass was harvested for forage. Switchgrass herbage mass and nutrient removal were greater in 2014 than in 2015. Our findings showed that N fertilizer rates for switchgrass under rain‐fed conditions need to be adjusted on the basis of expected herbage mass produced, hay value, and prior year N removal rates.