bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Backstepping Approach for the Attenuation of Torsional Oscillations in Drill Strings
Authors: Ullah Farooq Kifayat , Duarte Franklyn , Bohn Christian
Published: March 2016

A common problem in the petroleum drilling process is the torsional oscillation generated by the friction present during the cutting process. Torsional oscillations in drill string are particularly difficult to control because the drill string is an underactuated system, it has a very small diameter to length ratio and it is driven at top end with the cutting process at the other end. These factors make the drill string prone to self-excited torsional vibrations caused by the stick-slip of the cutting bit. The system is modeled as a torsional pendulum with two degrees of freedom, where the upper inertia models the top drive and also part of the drilling pipes. The bottom inertia models the bottom hole assembly (BHA). The drill is considered to be a massless torsional spring-damper. The drill string is subjected to friction, which is formulated using a dry friction model. The friction model takes into account Coulomb friction, stiction and Stribeck effect. The latter friction component is the main nonlinear phenomenon that introduces negative damping at the bit; it leads to self-enforcing stick-slip torsional oscillations.In the approach of this work, for the attenuation of these self-excited oscillations a recursive backstepping control strategy is used and it is carried out in continuous time. The main contribution of this work, which is different from the backstepping approaches reported in the literature, is to use a nonlinear/artificial damping as virtual control input. The stability of the system has been proven in the sense of Lyapunov. The goal of the proposed algorithm is to deal the underactuation of the system and to provide a good response for different operating points. The effectiveness and robustness of the controller has been tested in simulations.
Overcoming Shallow Hazards in Deepwater Malikai Batch-Set Top-Hole Sections with Engineered Trimodal Particle-Size Distribution Cement
Authors: Goenawan Jessica , Goncalves Rodrigo , Dooply Mohammed , Pasteris Mathieu , Heu Tieng-Soon , Chan Lakmun , Bhaskaran Sunderesan , Hinoul Wim
Published: March 2016

The well construction strategy for the Deepwater Malikai project, Malaysia, included 36-in. structural pipe jetting and 13 5/8-in. surface casing riserless cementing for top-hole sections with the objective for further development of lower sections with tension leg platform (TLP). Cementing of the 17 ½-in. surface hole mainly dominated by shale formation and penetrating multiple shallow faults required isolating shallow gas sands by bringing top of cement to the seabed, thus meeting the well integrity requirement stipulated by the Malaysian Petroleum Management (MPM).

The cement slurry design for the 13 5/8-in. casing with riserless mud recovery system includes selection of lightweight trimodal particle-size distribution cement blend optimized with a gas migration control agent and low-temperature dispersant. This mitigates dynamic losses in unconsolidated formations and faults having narrow margins between pore and fracture pressures. Cement slurry achieves faster compressive strength and static gel strength development at lower seabed temperature, preventing casing subsidence and providing good shoe strength. The cement job design respects density and friction pressure hierarchies, providing flat fluid interfaces between successive fluids pumped, combined with optimal casing standoff and displacement efficiency ensuring effective mud removal in highly deviated large-annulus top-holes.

This paper will discuss the extensive laboratory testing employed to qualify the engineered trimodal lightweight cement slurry design and effective mud removal strategy fit for the applications on the seven batch-set top-hole sections, achieving zonal isolation requirement.
Optimized Well Performance Through Stage Fracturing and Coiled Tubing Perforations and Isolation Operations in a Horizontal Tight Gas Reservoir: A Case Study
Authors: Anand Abhijeet
Published: March 2016

Coiled tubing (CT) services in India are positioned as highly tailored services with operations such as cleanout, nitrogen kickoff, and matrix stimulation in vertical or slightly deviated well. With the advent of horizontal wells in India, the scope of CT applications has increased considerably, especially for multistage fracturing in tight reservoirs.

This paper deals with well performance optimization in a tight gas reservoir in the Cambay basin situated along the western coast of India. Most of the reservoirs in the basin are very low permeability, and hydraulic fracturing may be the only way to achieve economic production from the reservoirs in most cases. The successful execution implied tapping into the unconventional gas reservoirs in India, which are expected to account for 75% of gas production in India by 2035. The plan was to fracture stimulate eight zones in four stages and later mill the isolation plugs to put the well into production from all eight zones. An innovative perforation technique of using dual firing head guns—an electronic firing head and circulation ball drop-activated firing (CBF)—in the same run to selectively perforate two clusters was used.

The presence of gas in the CT-tubing annulus while perforating the upper formations and the adequate isolation through the flow-through plug to provide appropriate pressure differential for the CBF were the major challenges faced whilst perforating. Previous failure in the offset well was carefully analyzed to identify the root cause and come up with appropriate job design and operating procedures. The job was designed to keep backpressure in a balanced condition to the reservoir pressure to prevent any inflow of gas through plug, and the electronic firing head was optimally programmed above the cushion reference pressure. A rise in the wellhead pressure and shock at the wellhead were the surface indications observed for both the electronic and CBF firing heads while the latter also exhibited sudden rise and then drop in circulation pressures.

The project was executed in a defined timeline as per client expectations. The well was completed with eight fractures in four stages placing the designed amount of proppant. Initial production estimates have been very encouraging, with increased Oil Gas Ratio (OGR) leading to 20% greater production than forecast. This operation has opened new possibilities for the use of CT services in horizontal wells in the same formation.
First Application of Multistage Completion & Acid Fracturing in Deep Carbonate Reservoirs in Kuwait
Authors: Al-Muhailan Mohannad , Juma Shehab Adnan , Aljarki Jasem , Sounderrajan Mahesh , Hiray Niranjan , Patil Dipak , Desai Ankur
Published: March 2016

Drilling horizontal wells into a heavily fractured sour Jurassic reservoir and resorting to acid fracturing may be the key to unlocking substantial reserves of oil for Kuwait. Horizontal wells, while more technically challenging and expensive, will ensure fractures are encountered and acid fracturing will penetrate multiple large, oil bearing fractures to improve productivity. This paper highlights the well design, planning, challenges, operational complications and results of the application of multistage completion & acid fracturing in a deep carbonate reservoir in one of Kuwait's field. The aim of the application of such a distinctive completion was to enhance the production from horizontal well in low permeability carbonate reservoir in West Kuwait.

A series of directional technologies and techniques were used in this application. These included a benign build profile, use of RSS motors in kick-off, curve and drain hole for enhanced steering capabilities, lateral drilling with PDC bits. The ability to drill the well without gains or differential sticking was a major challenge and one which was addressed with the close control of fluid design, mud weight window and hole cleaning policy.

A horizontal well was drilled to a TD of more than 15,500 ft with 7 casings policy with one sidetrack. In view of the multistage completion, which requires the hole to be clean of any debris so that the hydraulic ports and ball seats remain obstruction freefor allowing droping of balls, a conscientious decision was made to lower a 7 ¾? tie-back prior to lowering completion. The operations involved a series of steps performed for the first time in Deep Drilling with primary consideration to limit generation of metallic debris while employing judiciously the use of cleanup tools to get rid of the drilling generated metallic fines. This was followed by a simulated reamer assembly trip performed to ensure the successful lowering of completion assembly.

The paper discusses the challenges of horizontal drilling through formations prone to differential sticking, preparation of the hole for and lowering of multistage frac completion and fracturing. The well yielded favorable results with high oil production which showed great potential for increasing Productivity. While such completion will lead to enhanced productivity, lessons learned include among others a step ladder process to make lowering such a completion consistently successful.

Being the first application in deep reservoirs, the lithology has opened up a new dimension for tapping the full potential of the horizontal wells being drilled. This is likely to enhance production in future.
Non-Parametric Adaptive Regression Splines for Multisource Permeability Modeling in a Sandstone Oil Reservoir
Authors: Al-Mudhafar Watheq J. , Al-Khazraji Ahmed Khalil
Published: March 2016

Different from the imposed linear-relationship in multiple linear regressions, Multivariate Adaptive Regression Spines (MARS) is a nonparametric regression procedure that automatically fits the relationship between variables taking into account non-linearity. In this paper, MARS was adopted for multiscale construction of a relationship between core permeability given the Computer-Processed Indicators (CPI) of multiple well log records in a sandstone reservoir.

In MARS, a set of coefficients and basis functions, which are driven for the regression data, are used to construct the relationship between response variable (core permeability) and predictors (well log data and lithofacies). Different from other techniques, MARS is suitable for high dimensional predictors (multiple predictors) because the basis functions partition the input data into regions, each with its own coefficients set. Additionally, MARS has the ability of overcoming the possible outliers that might be available in the given data set. Likewise, MARS automatically eliminates the predictors that have no influence on the response.

The Computer-Processed Indicators (CPI) encompass: water saturation, shale volume, and neutron porosity. Lithofacies of sand, shaly sand, and shale were also included, in the modeling, to provide three different models given these discrete lithofacies classes. Consequently, MARS algorithm has proven its efficiency to model the distinct scales and construct the non-linear relationship between core permeability and CPI log data, given the lithofacies, by providing accurate coefficient estimation and prediction.

The MARS results were compared with the common approach of Generalized Linear Model (GLM). MARS led to much more accurate modeling and prediction than GLM as the coefficient of multiple determination was much higher and the root mean square prediction error was much less than the GLM. Accuracy of MARS algorithm came from taking into account the non-linearity between data into modeling; GLM consider simple linear relationship to fit the distinct scales data.
Eliminating Sustained Casing Pressure in Well Abandonment
Authors: Obodozie Ikenna E. , Trahan Scott J. , Joppe Lambertus C.
Published: March 2016

Sustained casing pressure (SCP) in oil and gas wells can result in leakage to the seabed if not properly checked during the final phase of the well life cycle. The escape of well fluid to the seabed as a result of SCP can lead to significant environmental damage, if not properly managed by the operator.

A recently developed innovative technology can drastically reduce the cost of sustained casing pressure mitigation during well plug and abandonment (P&A). The non-removal of the inner casing string before potential SCP sections are milled translates into savings for the operator. This specialty tool is designed to go through riser restrictions and pass through restrictions in the production casing internal diameter to mill the sustained casing pressure section in the intermediate casing. The mitigation of SCP in a single annulus is a challenging operation. In some cases, SCP exists in multiple annuli and can be more challenging because the removal of steel from the well is an expensive operation. The high-expansion section mill has been deployed in combination with improved milling technology in offshore well abandonment and has lowered the cost of well P&A.

The catastrophic impact of losing well barrier elements as a result of sustained casing pressure migration must be prevented. The cost of achieving this in some cases can be more than the cost of constructing a new wellbore. Moving forward, the industry will benefit from this technology by having the ability to mill a casing string section within a section. This capability eliminates the existing practice of performing several cut-and-pull attempts and/or casing milling, followed by a section milling operation.
Study on Longitudinal Vibration of Casing String in Deepwater by Riserless Drilling
Authors: Deng Song , Fan Honghai , Liu Yuhan , Liu Jinge , Tian Deqiang , Peng Qi , Ren Weiyan
Published: March 2016

The paper reviews the whole project and introduces the casing string structure of Riserless Drilling. Then it establishes the shallow Riserless Drilling longitudinal vibration model based on vibration theory, soil mechanics, fluid mechanics. We assume the soil layers around the casing are homogeneous, isotropic and saturated cohesive soil, and the earthquake force is harmonic excitation force. And the harmonic excitation force is at the bottom of the soil layers. Meanwhile, it also considers flow friction of drilling fluid in well bore. Based on this, this paper analysis the longitude forced vibration load of casing string by Riserless Drilling and gets its results. At the same time, this paper simulates the results through Abaqus software and compares it to the calculation results. And the results show that the earthquake degree, and the depth of casing is the main factors of longitudinal vibration of casing string of Riserless Drilling while the rate of drilling fluid has little effect on the vibration.
Integrated Simulation Based on Multiphysics Analysis, Virtual Reality, and Hardware for Offshore Installation, Operation, and Maintenance
Authors: Roh Myung-II , Ham Seung-Ho , Kim Ki-su , Zhao Luman
Published: March 2016

The simulation is being widely used to asses the safety and applicability of various offshore works. For this, some technologies can be considered to implement a simulator for offshore applications such as installation, operation, and maintenance. For more realistic simulation, an integrated simulation interface is proposed in this study by incorporating three different kinds of technologies; multiphysics analysis, virtual reality, and hardware. The proposed interface consists of an analysis module, a visualization module, a motion platform module, a network module, and so on. Using the proposed interface, we can synchronize the simulation time and exchange data on the network through the middleware with a standardized data structure. To verify the efficiency and applicability of the proposed interface, it is applied to various simulations for offshore works. As a result, we can see that the proposed interface can be used to perform the realistic simulation for various offshore works in less time and effort.
Application of Artificial Intelligence for Water Coning Problem in Hydraulically Fractured Tight Oil Reservoirs
Authors: Kalam Shams , Alnuaim Sami Abdulaziz , Rammay Muzammil Hussain
Published: March 2016

Artificial intelligence is playing a vital role in oil and gas industry. In this paper a new procedure and a unique statistical model has been developed to predict critical oil rate at any hydraulic fracture perimeter and reservoir property for Tight Oil Reservoirs (TOR) containing hydraulic fracture under water coning issue. The new approach uses numerical simulation and Artificial Neural Networks (ANN). Simulating the coning behavior is an expensive and time consuming technique. Therefore, there is a need for a readymade correlation which can help as a good quick estimate.

This research work exhibits a 3D simulation model, which has run for different ranges of fracture conductivity, kf*w (md-ft), reservoir permeability, k (mD), anisotropy ratio, kv/k, density difference, ?w-?o (lb/ft3), water oil contact, WOC (ft), fracture length, Lf (ft), fracture height, hf (ft) and oil viscosity, µo (cp) to find critical oil rate. Total number of 20,000 data points are obtained by the 20,000 number of simulation runs by coupling the commercial reservoir simulator with MATLAB. ANN is employed to obtain generalized correlation for critical oil rate in hydraulically fractured tight oil reservoirs.

Seventy percent of the simulated data points are used to develop the correlation and rest of them are used to validate and test the proposed correlation. Results show the good agreement with the unseen data. Correlation parameters are transformed to dimensionless form in order to get generalized correlation. Nonlinear regression technique was also applied to find the correlation, but ANN gives good results with lesser error as compared to non-linear regression. It is observed that critical oil rate highly depends on fracture half length, fracture height and fracture conductivity in the hydraulic fractured vertical oil well.
MWCNT for Enhancing Mechanical and Thixotropic Properties of Cement for HPHT Applications
Authors: Rahman M. K. , Khan W. A. , Mahmoud M. A. , Sarmah P.
Published: March 2016

Growing demand to drill high-pressure, high-temperature (HPHT) wells requires improved technology to overcome the HPHT challenges. Designing and testing for cost-effective cementing at simulated downhole conditions for HPHT gas and oil wells poses a challenge necessitating special consideration in the choice of cement slurry. A successful cementing job is dependent on how quickly and efficiently cement achieves its strength. Another critical aspect is to efficiently displace the mud out of the annulus by designing the cement slurry with desired rheology. Achieving desired mechanical and rheological properties of cement becomes harder and more complex at HPHT conditions.

A wide variety of admixtures are commonly mixed with the oilwell cement slurries to accommodate the extensive range of pressure and temperature and achieve enhanced mechanical and rheological properties. Carbon nanotubes are one of the most recent admixture options. This paper describes a study carried out to examine compressive strength and rheological properties (plastic viscosity, yield stress and gel strength) of oilwell cement slurries integrating chemical additives and multi-walled carbon nanotubes (MWCNT) at HPHT conditions.

The study determined that integrating MWCNT in oilwell cement led to substantial increase in the compressive strength values. The rheological properties of oilwell cement slurries are greatly reliant on temperature, water/cement ratio and the admixture used. The study indicated that using MWCNT in cement slurries improved the rheological properties of cement slurries and therefore their displacement efficiency in challenging conditions.
Tethered Steel Lazy Wave Riser Configuration for FPSO with Disconnectable Turret in Deepwater
Authors: Karunakaran Daniel , Sankar Subramanian , Frønsdal Magne , Baarholm Rolf
Published: March 2016

Recently turret-Moored Floating Production Storage and Offloading systems (FPSO) have been used in many deep water developments worldwide, with consideration of disconnectable turrets for harsh environment applications. This trend makes the interactions between FPSO and riser system more important. Further, Steel Lazy Wave Riser (SLWR), which is a compliant variant of the most commonly used Steel Catenary Risers (SCR), is becoming an attractive riser option.

The paper provides a review of the various riser systems that can be considered for turret-moored FPSOs, and specific emphasis on SLWR. A detailed case study of SLWR for a typical turret moored FPSO with disconnectable turret is presented. This system is described in terms of design and functionalities, the fabrication and installation methods are presented. The case study shows clearly that an improvised SLWR is an attractive alternative to be used for FPSO with disconnectable turret and is very efficient to fabricate and install in a very cost effective manner.

Pros and cons for SLWR are discussed, with consideration of the particular challenges of turret-moored FPSOs with large floater motions, hang-off geometry constraints at turret, hang-off loads, riser interferences, risers pre-installation, and turret disconnection constraints.
Heavy-Duty Cleanup: Caesium Formate-Based Microemulsions Make Light Work of a Tough Job
Authors: Moroni L. P. , Davidson M. , Lam J. , Goonoo A. , Twycross J. , Howard S. K.
Published: March 2016

Minimising drilling costs is an ongoing concern, especially with global uncertainty and volatile oil prices. One area in which costs can be reduced is in the wellbore cleanup phase. Inefficient cleanup can result in large volumes of liquid waste that must be treated or disposed of, particularly if a non-aqueous drilling fluid (NADF) is used. In addition, completion fluid costs can be significant, especially where high-density brines are required for wellbore safety. Improved cleaning efficiency can lead to significant cost savings.

Wellbore cleanups in high-temperature, high-pressure (HTHP) wells can be particularly challenging. Not only is high-density brine required to maintain hydrostatic overbalance to control formation pressures, the brine is often at or close to its saturation point. The selection of surfactants that function effectively in high-salinity fluids can be very challenging. Extensive laboratory testing must be performed to ensure compatibility between the cleanup spacer and the drilling fluid. The performance of the cleanup is then assessed through a series of bottle and viscometer sleeve tests to ensure the solids and metal surfaces were rendered fully water-wet.

A significant challenge when designing cleanup spacers is balancing excellent performance of oily residues and solids removal with thermal and chemical stability. Microemulsion cleanup spacers have been used to perform efficient wellbore cleanups in deepwater applications, resulting in reduced volumes of waste fluids. This paper describes the field application of a high-density caesium formate brine microemulsion cleanup spacer to efficiently displace and remove a high-density barite and manganese tetraoxide-weighted NADF. Results show that microemulsions exhibit excellent displacement and cleanup performance of a challenging drilling fluid. Microemulsion technology results in a quicker cleanup with reduced waste volumes, thereby minimising costs.

The high value of caesium formate brine means that maximising the recovery of this valuable asset is essential to justify the economics of the cleanup process. This paper describes the transfer of microemulsion cleanup technology used in deepwater environments to HTHP applications.
Structural Interpretation Based on the Application of Seismic Attributes - A Case Example in the Offshore of the Peninsular Malaysia
Authors: Shamsuddin A. , Shahar S. , Ghosh D. P. , Ngoc N. H.
Published: March 2016

Geological interpretation based on the seismic attributes can enhance the accuracy of the interpretation. According to Chopra and Marfurt (2007), seismic attribute is any measure of seismic data that can help in enhancing or quantifying features of interpretation interest. There are a lot of seismic attributes and it is hard to choose. The results are based on the computation of the seismic attributes on the offshore of the Peninsular Malaysia. The methodology of the seismic attributes starting from the condition of the data in order to get the best results from the computation of seismic attributes. The condition of the data might give high influence to the seismic attributes computation. Seismic attributes were computed based on the previous researchers' suggestions on the best seismic attributes that can be used to compute the structural features. Interesting structural features which are important in the geological interpretation like fault can be defined in this study area. Based on the results, there are a few types of the seismic attributes which were suggested are suitable and can be applied to the study area and there are a few types which are still can be in doubt and can be in debatable. As a conclusion, the applications of the seismic attributes need to be handled attentively as it might show artifacts. In this case, a few key wells need to be applied in order to validate the geological features especially structural features in this study area. The accuracy of the features can only be confirmed based on the well data for example FMI log. The approach of using various seismic attributes will introduce different types of interesting features for structural study, which might be beneficial in geological interpretation.
Multilateral Gravel-Pack Solutions for Single Wellbore Branches
Authors: Durst Doug G.
Published: March 2016

Drilling, completion, and production monitoring and control of multilateral wellbores in highly unconsolidated sandstone formations have been successfully achieved both technically and operationally in the recent past, helping to ensure that planned production rates and reserves are achieved.

Gravel packing lateral branches on multilateral wells is no longer challenging. Sound isolation of the main branch can preserve the mainbore of debris when milling the window and drilling the lateral, helping ensure seamless gravelpack operations. Stable junction isolation exists to support sand placement and subsequent reverse-out gravel pack operations in the main and lateral branches.

With respect to multilateral wells, one of the key factors in terms of determining whether or not a multilateral wellbore might be suitable for a given project is the size and type of sand control completion and technique that might be necessary. The use of conventional standalone screens combined with multilateral technology has a long and highly successful history. Where more sand control reliability is necessary, the use of gravel packs or frac packs in combination with multilateral wellbores, technology is now available and beginning to develop its own successful history.

In its current form, when combining advanced sandface completions with multilateral completions, gravel pack operations are subsequently followed by the installation of the multilateral and upper completions. As a result of a newly developed system, the junction completion can now be interconnected with the sand control operations in a single seamless operation.
Application of Test Simulation Technique in Deepwater Heavy Oil Reservoir
Authors: Zhang Junbin , Duan Yonggang , Chen Feifei , Li Zhenglan
Published: March 2016

Heavy oil reservoirs have became a key and difficult point as exploration and development of oil and gas goes deeper. Since deepwater heavy oil reservoirs are characterized by adverse fluid property and poor flowability resulting from low seawater temperature, conventional well test usually fails to gain expected crude sample and real formation data, leading to some problems for subsequent development. In view of two difficult issues during the deepwater heavy oil reservoirs test – flow assurance concern and decision-making difficulty in testing system, application of appropriate test technologies and techniques are of great importance.

Prior to the offshore test, an integrated approach to modeling and designing operating conditions was described. The feasibility of available technical solutions in relation to enhancing the low wellhead temperature conditions was discussed based on the wellbore temperature and pressure features derived from the analytical modeling, and a test technique (integrated progressing cavity pump (PCP), heating sucker rod and insulated tubing) applicable to deepwater heavy oil reservoir was recommended. Then, drilling-stem test (DST) was carried out to an exploration well with two oil layers and one gas layer which is located in southwest of Congo sea with the recommended test technique.

Simulation results demonstrate that the advantages of the compound technology – electric heating, PCP and insulated tubing are far greater than using insulated tubing or heating sucker rod alone. Compound technology decreases the frictional pressure loss of the producing fluid due to its capability of maintaining high and uniform wellbore temperature. Interactive tubing conveyed perforating (TCP) and DST was conducted with a testing program of thrice flow well and twice shut-in well. Insulated tubing assembly was employed from progressing cavity pump stator to the wellbore and the setting depth of the heated sucker rod was down to about 10m above the pump. Productivity information, representative crude samples and pressure/temperature information of the testing zone were obtained successfully.

The simulation technology and pilot test proved the feasibility of insulated tubing and electric heating PCP in deepwater heavy oil testing, providing technical guidance for further appraisal and development of deepwater heavy oil fields.
A New and Practical Model for Amount and Rate of Sand Production Estimation
Authors: Wu B. , Choi S. K. , Denke R. , Barton T. , Viswanathan C. , Lim S. , Zamberi M. , Shaffee S. , Fadhlan N. , Johar Z. , Jadid M. B. , Madon B. B.
Published: March 2016

This paper presents a comprehensive study on sand production with the objective to develop a practical sand production model to estimate amount and rate of sand produced. The study comprised three components; laboratory experiments, numerical modeling and field case study for model validation. An experiment program was carried out on seven weak sandstones with various strengths. The experiments were conducted on relatively large samples under realistic effective reservoir stress and drawdown conditions with oil and gas flow. The large sample size allowed a meaningful amount of sands to be produced with minimum boundary effect. Real-time borehole monitoring using a borescope and X-ray CT scanning on the tested samples enabled rock failure and sanding mechanisms to be investigated. The laboratory experiments were simulated by numerical modeling using discrete element and finite difference methods. A sand production quantification model was developed by correlating the critical plastic volume obtained from the numerical modeling with the cumulative amount of sand produced from the sanding experiments. The sand quantification model was applied to a field case study aiming for model validation. The modeling result has been so far consistent with field observations.
Intrusive erosion Probes on Subsea Equipment - Design and Placement Considerations
Authors: Leong Melvin , Sanchis Arnaud
Published: March 2016

Sand monitoring equipment provides the operator with integrity management information on the condition of subsea production systems and guidance on the erosion trends over the field life. However the placement of such equipment, in particular the intrusive erosion probe (IEP), is often carried out at sub-optimal locations. This is sometimes a result of space limitations on the equipment on which it is mounted on. This paper discusses the current practice on the placement of the IEP and potential problems that may arise from a poorly located IEP. A discussion on the possible mitigation measures is provided. Where necessary these are illustrated through the use of good design and analysis practices.
A Comparative Study for the Prediction of Ultimate Tensile Strength in Flexible Pipes
Authors: Yim Ki-Ho , Jang Beom-Seon
Published: March 2016

A flexible pipe consists of several layers which have various materials and different functions. For a new design of flexible pipe, the structural response on external loads will vary depending on the characteristics of each layer. In order to compute the behavior of flexible pipe, a cross-section analysis is required. Theoretical, numerical, and experimental approaches can be used.

The prototype test is most reliable way to find the characteristics and strength of flexible pipe, and it is mandatorily required in most of applications. From experiments, failure mechanism and utilization of stress in each layer against tensile loads can be evaluated. However, it is limited in the number of tests due to the cost and the capacity of instrument.

The theoretical and numerical methods are efficient to the new flexible pipe design, and many previous researchers demonstrated that those give reliable solutions.

In order for prediction of the ultimate tensile strength, the non-linear material property of all layers should be considered. However, application of the non-linear material to the theoretical analysis of flexible pipe can rarely be found.

In this paper, a theoretical model using an equivalent orthotropic shell is developed considering the non-linear material of tensile armour in order for the assessment of the ultimate tensile strength of flexible pipe. Comparatively, FE models are also developed considering all contacts between layers and nonlinear materials for each layer. The 2.5? ID flexible pipe provided in the previous research is used for both models. From the comparative study, both results show good agreements with respect to the elongation and equivalent stresses depending on the tension. Similar ultimate tensile strengths of the flexible pipe are obtained.
New Rock Physics Template for Better Hydrocarbon Prediction
Authors: Hermana Maman , Lubis Luluan A. , Ghosh Deva P. , Sum Chow Weng
Published: March 2016

Understanding the behavior of elastic properties to get the best discrimination on lithology and fluid prediction is the most important knowledge to minimize the pitfalls in the interpretation. Rock Physics Template (RPT) which is geologically constrained rock physics model can serve the information about the lithology and fluid separation; hence it can guide the interpreter to reduce the pitfalls in prediction and misinterpretation. The objective of this paper is to show the performance of new RPT in discriminating the lithology and pore fluids. The new RPT has been developed based on SQp and SQs attributes. These attribute were derived from attenuation–rock physics approximation. The new RPT was tested on soft sediment and cemented model and it was also applied on the real dataset from a field in Malay Basin. The performance of new RPT on lithology and pore fluid separation was compared with the existing RPT generally used in the industry. The results show that the new RPT which is based on SQp and SQs attributes give better separation in lithology and hydrocarbon prediction. The lithology effect was separated in the SQp domain and pore fluid was separated in the SQs domain which are both domain are orthogonal to each other. The implementation of this RPT on the real data shows that the gas sand separated clearly from wet sand and coal layer. The pitfalls due to the coal masking can be solved by implementing these attributes. The lithology and pore fluid were separated optimally. This new RPT provides an optimum separation on lithology and pore fluid effect. Pitfalls due to Coal mask can be separated properly; hence this new technology potentially can be used to reduce the pitfalls and uncertainty in hydrocarbon prediction. Further improvement is still required on the extended applications of this new technology on other cases such as low resistivity low contrast pay prediction.
Emerging Technologies and Workflows in Digital Oil Field
Authors: Chanana P. , Soni T. M. , Bhakne U.
Published: March 2016

The need for the petroleum industry to understand more about subsurface and surface operations has driven it to gather greater data volumes of various types at high frequency. However, searching relevant information from this data is quite complex and time consuming, complicating the decision making process.

With emerging technologies, business processes are improving and the industry experts are able to design more intelligent, advanced and automated workflows. These advanced workflows are required to bridge the gap between various inter-linking operations and to reduce time lag. This results in reducing the time involved in decision making and improving the quality of decision. In the same way, managing data has advanced to a great extent with evolving technology. Data management, which includes data gathering from various sources, data cleansing, validating and analyzing, is required to manage huge amounts of data and take quick actions for better business benefits. The need for integration of data management and improved business processes in the oil and gas industry has given rise to several Digital Oil Field (DOF) implementations over the decade.

Digital Oil Field, an evolving technology, has transformed from a reactive approach to a proactive approach. In the past decade, DOF involved installing devices such as sensors on the field to gather data. Now, it has moved to visualizing data on dashboards, monitoring, and making operations effective. Soon we will have smarter solutions where systems will make decisions and indicate potential means to overcome issues with the help of best practices and predictive analysis.

This paper aims to review the work done in the sphere of DOF over the decade. Basic DOF architecture and data flow in business processes from data capturing to visualization are also explained briefly in this paper. The benefits of DOF technologies to the petroleum industry, the success factors of DOF and its future direction are also discussed.
Study about Statistical Approach in External Turret Mooring Analysis of FLNG
Authors: Hayashi T. , Ando T. , Kato S. , Yukawa K.
Published: March 2016

There is no common procedure guidance how to evaluate extreme value from dynamic time-domain simulation of turret mooring system which is mostly applied to FLNG positioning system. In this paper, the time-domain dynamic simulations using turret moored FLNG model in different water depth are carried out and various statistical analysis methods are applied to each 3 hours simulation to obtain evaluated extreme line tension.

By the case study results, the paper presents the investigation about the most suitable statistical analysis procedure to evaluate extreme response of time-domain turret mooring analysis. In addition, the detailed analysis procedure in case of storm that is wave and wind force directions are rapidly changing condition is also investigated based on time-domain simulations.
An Integrated Reservoir Modelling Approach in Constructing a Representative Thin, Heterogeneous Clastic Reservoir - Case History
Authors: Das Apurba Kumar , Arsanti Dian , Ghadami Nader , Tunio Kamran Haider , Dou Ali Asem Mahmoud A
Published: March 2016

An integrated modeling approach was used in a thin, highly heterogeneous complex clastic reservoir to build a more robust three-dimensional geo-cellular model by incorporating all available data from geoscience disciplines such as geophysics, geology, petrophysics and reservoir engineering. The model was used to replicate actual reservoir flow dynamic and generate optimum development strategy.

The early versions of the model relied heavily on seismic attributes to populate the reservoir facies. The poor seismic resolution of this thin reservoir has resulted in a patchy facies distribution which could not represent the actual fluid behavior during dynamic modeling. An alternative modeling approach was followed which populates the sand based on net sand mapping which honors the conceptual depositional model of this reservoir. As a result, this approach was used to improve the static model based on actual observed data like pressure and injection response in nearby producers and performance of well behavior.

A more reliable reservoir model was built after a lot of iterations between static and dynamic models without changing basic conceptual geology. The characterization of the reservoir as fluvial/deltaic mouth bar lobes has helped to capture a realistic heterogeneity level of the reservoir which made the history matching process much easier. Critically well-wise production performance analysis was conducted before proceeding to dynamic modeling. Production allocation anomaly was observed in few wells and necessary weight has been given to these wells during history matching. One of the key parameters that needs high attention particularly for reservoirs under waterflooding is relative permeability. Because of lack of availability and high uncertainty of relative permeability data in this reservoir, a systematic sensitivity analysis was performed on end point relative permeability and Corey parameters. As a result, the impact of each examined parameter on reservoir performance was scrutinized. The concept of producer injector pairing was used during history matching process and satisfactory history match achieved with minimum property modifiers.

A real case example was used to introduce an alternative modeling approach for thin, below seismic resolution clastic reservoirs to achieve a satisfactory history matched model. The presented approach would provide rigorous and sound reservoir models. The sensitivity analysis on relative permeability parameters expedites to the better understanding of flow behavior of the reservoir.
Application of Game Theory for Optimizing Drilling Cost Reduction Programmes
Authors: Ajimoko O.O. (Tayo)
Published: March 2016

Most drilling cost reduction initiatives are reactionary, unsustainable and ultimately fail. Usually the failure is neither due to incompetence nor is failure of planning the root cause and neither is it due to a lack of follow through on the plans and strategies. However, they fail because of inefficient opportunity framing and inadequate understanding of the underlying human interactions involved. The pull and push effects of the cost reduction agents is not also fully analysed.

Because most drilling cost reduction initiatives are reactionary, the planned time-frame is typically immediate to short term and the situation of things typically return to the status-quo ante or normalcy shortly afterwards. Consequently, the resultant effect on the organization is not readily apparent and when manifestsed, it is felt mainly in the operational domain. Overall, it results in more inefficiencies at greater costs over the long term. This is usually masked by early apparent gains reflected in the cost saving line item numbers.

Drilling Cost reduction is a change event usually involving major disruption in the routines of the affected personnel (direct and indirect), work segments, service providers and operating philosophies and practices. It therefore requires robust and rigorous management of change protocol.

Game theory is a type of decision theory in which one's choice of action is determined after taking into account all possible alternatives available to an opponent playing the same game, rather than just by the possibilities of several outcomes. It is therefore a useful tool for analysing and anticipating the potential outcomes of a cost reduction initiative to effectively manage disruptions and the resultant inefficiencies. It provides a framework for properly considering the unobvious but highly possible variables at play.

This paper will present a conceptual framework for evaluating a hypothetical drilling cost reduction program. For the purpose of this paper, the rational players / agents will be the service companies, the national government and the Oil and Gas Company. Principles and observations from Decision Theory, General Equilibrum Theory and Mechanism Design Theory will be used as anchors for predicting the possible outcomes of the game.
Monitoring Strength Reduction in Sandstones Associated With Fluid Substitution Using Advanced Rock Mechanics Testing
Authors: Sarout J. , Dautriat J. , David C.
Published: March 2016

This paper presents a novel rock mechanics testing method for remotely monitoring, detecting and assessing mechanical weakening and possible sand production in sandstone reservoirs during water flooding or during drilling with water-based muds. Rock mechanics triaxial tests are conducted on sandstone reservoir samples subjected to realistic in situ stresses, pore pressure, and temperature. During these tests, in addition to the conventional stress and strain monitoring techniques, the new approach involves a combination of ultrasonic and micro-seismic monitoring techniques allowing for a remote detection and spatial localisation of the possible mechanical weakening that ultimately leads to sand production. The original testing protocol allows for the substitution of the in situ fluid by a water-based fluid with minimal impact on the in situ effective stress in the rock sample. The weakening effect of the substituting fluid can therefore be discriminated from any mechanical artefact associated with a possible reduction in the effective pressure during the substitution. Thanks to the conventional stress-strain monitoring technique, it has been observed that (i) the strength and static elastic moduli decrease when water saturates the pore space; (ii) the injection of water in a critically loaded sample initially saturated either with air or inert oil induces a drastic increase in the creep rate and the development of a mechanical instability. Thanks to the ultrasonic and micro-seismic monitoring of the fluid substitution process, it has been observed that (iii) the mechanical instability is mainly localised in the water-flooded zone; (iv) this instability corresponds to a loss of cohesion between the sandstone grains; (v) during oil substitution by water, the insability is delayed in comparison with the water injection in the dry sandstone and the loss of cohesion is less pronounced. This loss of grain-to-grain cohesion is expected to lead to sand production in weakly consolidated siliciclastic reservoirs. In addition, the injected fluids significantly affect the ultrasonic P-wave velocity: (vi) increases during oil injection; (vii) decrease during water injection. This helps in detecting the advancement of the fluid front within the rock's pore space.