bluuebunny/crossref_metadata_2025_split huggingface dataset:
Managing Uncertainties and Surprises in Carbonate Gas Reservoir through Lower Completion Design Optimisation
Authors: Bakar Hasmizah , Bernard Caesar Sokate , Shata Karim Ahmed , Shaedin Muhamad Ridzuan , Roh Cheol Hwan , B M Khir Khairul EzeeAzreen 
Published: October 2018

Abstract
There are three (3) requirements of any completion in common; safe, economical efficient and reliable. 76% of PETRONAS CarigaliSdnBhd's wells in Sarawak Gas are completed in porous, heterogeneous and complex carbonate reservoirs. Four (4) types of lower completions are implemented for carbonatereservoir: barefoot, open hole Pre-Drilled Liner (PDL) with isolation packer, open hole blank liner with isolation packer with post perforation and cemented cased hole. This paper shares the best practices, lessons learnt, risks and performance from recent experiences at field FX, FY and N which are used to support the proposed lower completion design and selection criteria workflow.
Other than risk of wellbore collapse, early water breakthrough and fluid losses to formation, the provision for zonal isolation, cost, well productivity and complexity of operation have been part of the critical elements to be considered in the proposed process workflow from planning to execution phase. Dedicated studies such as wellbore stability analysis, critical drawdown requirement over time and well modeling are also being carried out to provide enhancment of lower completion design.
This selection criteria and lower completion design process flow has been applied in recent FY field development campaign which resulted 32% of cost saving in 3 horizontal wells and met the production gas target with zero Lost Time Injury (LTI).
The other particular merit of this paper is to share some the best practices and lessons learnt from FX, FY and N field case histories and the approaches taken to manage the risks.
A Successful High-Ratio Hole Opening Utilising a Dual Underreamer Saved Drilling Time in a Shale Gas Exploration Well
Authors: Abdila Sayid Faisal , Anuraga Edo , Prayitno Sugeng , Yoan M. R. , Noviasta Bonar , Pratama Kevin , Febriarto Hendriyan , Astasari Kanya , Agustina Imma 
Published: October 2018

Abstract
Well M is a vertical shale gas exploration well in Indonesia. The presence of overpressured shale formation dictated the requirement to have a 16-in. intermediate casing string between the 20-in. and 13.375-in. casing to cover an approximately 350- to 1000-m measured depth (MD) interval. The mandatory logging operation in all hole sections required a 12.25-in. pilot hole to be predrilled, to enable the logging tool to get a good measurement quality, before it was enlarged to 17.5 in. for setting the 13.375-in. casing. Several hole opening challenges needed to be considered in this operation: 1) The hole opening tool should pass the 16-in. casing inside diameter (ID) restriction (14.936 in.); 2) the tool needed to be applicable for hole opening with an existing pilot hole (bi-center is not a feasible option); 3) the tool should be able to open the shoe track from 12.25 in. to 17.5 in. for 13.375-in. casing run assurance; and 4) the hole opening needs to be as efficient as possible to eliminate multiple runs.
A dual hydraulically expandable underreamer was proposed to answer all those challenges. The configuration consists of two underreamers with different opening capability, which satisfies the high-ratio opening requirement. The lower reamer opened the hole from 12.25 in. to 14.75 in., and the upper reamer further opened the hole from 14.75 in. to 17.5 in. Because running a tandem underreamer is not a common operation, a thorough vibration analysis must be performed to ensure the tool reams in a stable condition, not only to avoid downhole tool failure but also to produce a smooth borehole. Hydraulics optimization is also critical to ensure both underreamer cutter blocks are fully opened during the run.
The tandem underreamer successfully opened the hole from 12.25 in. to 17.5 in. in one run to the section TD from 980 to 1623 m MD (a 643-m interval). At the surface, both underreamer cutter blocks were still in a good condition with 0-0-NO cutter dull and in gauge condition, which showed a good stability. This is also supported by the success of the 13.375-in. casing run to bottom without any issue, indicating a good and smooth borehole. The tandem underreamer method successfully achieved the high-ratio hole opening objective and saved drilling time by eliminating the unnecessary trip for having two separate underreaming runs.
The underreamer tool mechanism and the criteria by which the dual underreamer configuration became the solution to the main challenges in this case study were documented. The study showed that the prejob engineering work (vibration modeling using dynamic finite element analysis and hydraulics modeling) was a critical part in the success of the operation.
Rock-Breaking Mechanism Study of Axial and Torsional Impact Hammer and its Application in Deep Wells
Authors: Liu Shubin , Ni Hongjian , Wang Xueying , Wang Yong , Wang Peng 
Published: October 2018

Abstract
A brand new impact hammer–Axial & Torsional impact hammer (producing high-frequency axial and torsional impact forces simultaneously)–has been developed to improve the penetration rates and eliminate stick-slip vibrations in deep and ultra-deep wells. This paper presents its rock-breaking mechanism and evaluates its field application effects.
Based on the finite element method, a numerical model was first proposed to investigate the rock-breaking processes of a single PDC tooth under axial, torsional and axial & torsional impact forces respectively. The simulation results show that the axial & torsional impact drilling method can break rock with least mechanical specific energy and increase the rate of penetration (ROP) significantly. The mechanism is that the axial component of the compound impact force can increase the penetration depth of PDC teeth into rock and enlarge the rock-breaking volume, and that the torsional component facilitates to reduce stick-slip vibrations and prohibit premature failures of bits.
An Axial & Torsional impact hammer was then developed according to the principle of modulating hydraulic pulses. The hammer has been used in 20 deep and ultra-deep wells in western China, achieving 105.1%~163.4% higher ROP compared with the average ROP in the same block. Besides, the drilling process became more stable and the lives of PDC bits were greatly increased. This paper presents a comprehensive comparison of the penetration rate, torque fluctuation, bit wearing degrees and cuttings shape between this impact tool and other tools used in offset wells.
Finally, the structure of the new hammer is simple and reliable, and it is also convenient to maintain.
Assessing the Impacts of Groundwater Intrusion to Production Efficiency and Proposing Solutions to Enhance Oil Recovery from Fractured Basement Reservoir in SuTuDen Field, Offshore Vietnam
Authors: Tran Xuan Van , Nguyen Tuan Van , Nguyen Tuan , Nguyen Kha Xuan , Thai Ngoc Ba , Truong Thanh Quoc 
Published: October 2018

Abstract
Based on the observed phenomenon of formation water intrusion in SuTuDen oilfield, i.e., high reservoir pressure, high constituent percentage of formation water in produced water, stable isotopes tracing, as well as strong-water drive mechanism confirmed by matching & calibrating the production parameters, the authors assessed the impacts of water drive to the production and proposed methods to enhance recovery.
The results of water analysis with low TDS (12g/l) indicate the formation water accounts for a significant ratio of the produced water.
Among factors affecting production efficiency, the critical ones are fault-fracture characteristics, origins of water, range of hydrodynamic relationship, design plans and well completion. In order to mitigate the negative impacts and increase the positive impacts of these factors, a series of intervention solutions must be considered including combined ESP-Gaslift installation, gas assisted gravity drainage, water or gas injection in selective zones, infill drilling in poorly connected areas.
The basement reservoir SuTuDen oilfield is affected by natural water aquifer hence it is necessary to implement recovery solutions such as adjusting the design, maintaining the reservoir pressure, in-fill drilling, artificial lift, stimulating the near-wellbore zone, optimizing the production-injecting regime.
When the wells have already been invaded by water, it is very difficult and costly to maintain the cumulative production. Therefore, the mitigation measures should be applied early from the design stage, especially the compatible operating regime, help reducing the water invasion and achieving optimal production.
The result of the methods should allow an increase in the overall recovery factor from 36.1% to 39.8%, equivalent to 18.52 MMbbl.
Aligning Field Development Options to Harsh Economic Conditions in an Offshore Brownfield in Malaysia
Authors: Kumaran Prashanth , Mandal Dipak , Kadir Zairi , Kamat Dahlila , Ibrahim Ramli , Maldonado Jorge , Iskenova Gulnara , Sharma Sachin K. , Rahman Mohd Ramziemran , Chabernaud Thierry , Ceccarelli Tomaso , Syahir Ahmad , Djarkasih Fredy , Rahman Nor Nabilah , Moreno Juan Carlos 
Published: October 2018

Abstract
In the current period of industry downturn, creating and executing opportunities to develop an offshore brownfield has become more economically challenging. This paper describes the technical, commercial, and operational aspects that helped in achieving an established economical cut-off for project sanction. The project will enable sustaining field average oil production above operational economic limits thereby maximizing field life. With the prevalent low oil price conditions, the economic threshold for projects sanction and execution has reduced. The asset team faced a challenge to achieve a UDC threshold of USD16/bbl. Multi-disciplinary team was tasked to look at key aspects to improve project commerciality. Subsurface recovery potential was assessed thoroughly to evaluate the impact of subsurface uncertainty, and evaluate the impact on well designs on the project cash flow. Wells were designed to tap multiple reservoir targets to minimize subsurface risk through existing facilities to maximize ullage. The wells were drilled from new slots via small deck extension instead of the high-risk slot recovery option, which helped to reduce the Capital Expenditure (CAPEX). Fit-for-purpose and cost optimized wells were designed by minimizing automation (i.e.: ICVs, PDGs, etc.) which also reduced operating risk and cost. Multiple sands were targeted in different compartments with different pressure system, hence planned not to commingle production. Hence, only one primary reservoir was completed, with other zones kept behind casing for future intervention with bottom-up production strategy. This helped deferring the project investment as this was in the intervention cost in Operating Expenditure (OPEX) which helped to improve the project economics. Further cost savings were achieved by accelerating the project in order to achieve synergy with an upcoming drilling campaign. The reduction of the overall project CAPEX, thus allowed the project to be commercially feasible and technically sound for execution. In addition, the team has also established a reservoir management plan with mitigation plan to deal with the main subsurface and surface risks. The out of box solution of optimized field development plan for complex offshore brownfield with limited facilities modification, while being cost conscious but still ensuring technically sound concept proved to provide the answer for sustainable production growth in S Field at low oil price environment. This paper will also highlight the key lessons learnt and obstacles which were observed during the execution of the project are expected to become guidelines for future low cost projects in this region.
Simultaneously Drilling and Underreaming Directional Topholes with Underreamer Below Mud Motor Save a Trip in Collision-Free Operations: Offshore Sakhalin Island Case Study
Authors: Kasumov Ruslan , Shakirov Irek , Gaisin Rim , Romanov Andrey 
Published: October 2018

Abstract
An operator was drilling complex big-bore gas extended-reach drilling (ERD) wells from an offshore Sakhalin Island platform. Because of the shallow gas anomaly presence beneath the platform, there was a requirement to set an intermediate casing or liner at ~375-m true vertical depth (TVD), which was between the 30-in. driven conductor at 170 to 175-m TVD and the next casing setting depth of 950 to 1065-m TVD. Due to the well complexity and completion requirements, conventional casing design with no underreaming operations was not an option.
Well reach and complexity significantly increased since the project started in 2007, which called for improvements in wellbore geometry. The wellbore geometry underwent few changes, concluding with the latest most favorable required for a 27 to 28-in. directional tophole out of a 30-in. conductor with the maximum bit size pass-through diameter of 25-in., and setting 24-in. liner at ~375-m TVD. Originally, these types of topholes were delivered in two separate trips. On the first trip, the 24-in. borehole was drilled with a mud motor bottomhole assembly (BHA), and on the second trip, underreaming-only operations were performed to obtain final borehole diameter. This operation required additional rig time and caused excessive vibrations during underreaming. A different type of underreamer was implemented successfully to eliminate vibrations, but it did not reduce the number of trips. The ultimate solution was to run the underreamer below a bent mud motor, enabling simultaneous drilling and underreaming of the directional top hole while steering the trajectory in a crowded subsurface environment. The presence of deviated conductors with 6 to 8° inclination at the shoe in all outer slots played a substantial role in overall success of the operation. It is very unlikely that the same results could be achieved if the outer slot conductors were straight.
Installing the underreamer below the mud motor worked successfully in five recent wells, saving a trip in each well. The tophole trajectory was effectively steered away from the offset wells, creating a no-collision-risk situation. A 24-in. liner was run to the planned depth and cemented. This technique was accepted by the operator for the major offshore project and used as the way forward for the remaining five outer slots.
The successful implementation of the simultaneous drilling and underreaming technique demonstrated the benefits and qualitative acceptance of using an underreamer below the mud motor for the directional tophole in this major Sakhalin offshore project. The knowledge and lessons learned from the project can be applied to other worldwide projects with identical or similar casing design requirements.
Effect of Crystal Modifiers and Dispersants on Paraffin-Wax Particles in Petroleum Fluids
Authors: Sun Minwei , Naderi Khosrow , Firoozabadi Abbas 
Published: October 2018

Summary
Petroleum fluids from shale light-oil and gas/condensate reservoirs generally have a high content of normal paraffins. Paraffin-wax deposition is among the challenges in shale gas and oil production and in offshore flow assurance. Low-dosage chemical additives can be effective in paraffin-wax mitigation because of their high efficiency and economics. These additives are divided into broad categories of crystal modifiers and dispersants with vastly different molecular structures and mechanisms in wax-crystal-particle stabilization and wetting. This investigation focuses on the understanding of the differences in the aggregate size and morphology of chemical additives, and it centers on (1) wax-particle sedimentation from diluted petroleum fluids in vial tests, (2) wax-crystal-particle-size distributions and morphology by dynamic light scattering (DLS) and polarized-light microscopy, and (3) the wetting state from the effect of water. In two of the three petroleum-fluid samples used in this work, there is no visible precipitation at the bottom of the vials at temperatures below the wax-appearance temperature (WAT). The microscopic image of fluids along the length of the tube shows that the wax-particle size and intensity increase from top to bottom. To observe precipitation, we dilute the crude with a hydrocarbon such as n-heptane. The sedimentation of wax is then observed. The petroleum fluids used in this work have very low asphaltene content, and there is no complication from asphaltene precipitation. Our study shows that a small amount of crystal modifier and dispersant can reduce crystal-particle size to the submicron scale, and change the crystal morphology. We investigate the differences in the mechanisms of dispersants and crystal modifiers in bulk. Water, which is often coproduced with petroleum fluids, can increase the effectiveness of dispersants significantly by altering the wetting state of the wax-particle surface. Such enhancement is not found in crystal modifiers. Both additives affect the rheology of petroleum fluids.
Analyzing the Well-Interference Phenomenon in the Eagle Ford Shale/Austin Chalk Production System With a Comprehensive Compositional Reservoir Model
Authors: Tang Hewei , Yan Bicheng , Chai Zhi , Zuo Lihua , Killough John , Sun Zhuang 
Published: October 2018

SummaryWell interference is a common phenomenon in unconventional-reservoir development. The completion and production of infill wells can lead to either positive or negative well-interference impacts on the existing producers. Many researchers have investigated the well-interference phenomenon; however, few of them attempted to apply rigorous simulation methods to analyze both positive and negative well-interference effects, especially in two different formations. In this work, we develop a comprehensive compositional reservoir model to study the well-interference phenomena in the Eagle Ford Shale/Austin Chalk production system. The reservoir model considers capillary pressure in the vapor/liquid-equilibrium (VLE) equation (nanopore-confinement effect), and applies the embedded discrete-fracture model (EDFM) for dynamic fracture modeling. We also include a multisegment-well model to characterize the wellbore-crossflow effect introduced by fracture hits. The simulation results indicate that negative well-interference impact is much more common in the production system. With a smaller permeability difference, the hydraulic-fracturing effect can lead to a positive well-interference period of several hundred days. The nanopore-confinement effect in the Eagle Ford Shale can contribute to the negative well-interference effect. We also analyze the impact of other factors such as initial reservoir pressure, matrix porosity, initial water saturation, and the natural-fracture system on the well performance. Our work provides valuable insights into dynamic well performance under the impact of well interference.
Pore-to Reservoir-Scale Modeling of Depletion-Induced Compaction and Implications on Production Rate
Authors: Sun Zhuang , Tang Hewei , Espinoza D. Nicolas , Balhoff Matthew T. , Killough John E. 
Published: October 2018

Abstract
The reduction of pore pressure caused by depletion can induce significant reservoir compaction, especially in unconsolidated reservoirs. Experiments using unconsolidated core samples are often sparse and costly. We develop a numerical approach based on computer-based simulations of rock samples and mechanical tests. The numerical sample consists of crushable grains simulated with the discrete element method (DEM) and the bonded-particle model (BPM). Model parameters are calibrated through numerical single-grain-crushing tests which reproduce the experimentally-measured sand strength. Grain crushing induced by the uniaxial strain stress path results in a pronounced reduction of porosity and permeability, which manifests more readily for samples with large grain size. The change of particle size distribution indicates that the high effective stress causes grain crushing and produces a significant amount of fines. We perform numerical uniaxial strain tests on numerical samples comprising stiff and soft mineral grains. Simulation results indicate that the presence of soft grains and inclusions (e.g. shale fragments) facilitates the grain crushing. Reservoir simulations, incorporating the change of porosity and permeability as a compaction table, show that the upscaled compaction can enhance production due to compaction drive but also reduces production rate by impairing the reservoir permeability. This multiscale numerical workflow bridges particle-scale compaction behavior and field-scale reservoir production. In this paper, (a) DEM simulations provide a useful tool to investigate compaction effects and complement laboratory experiments; (b) the multi-scale numerical approach can predict the depletion-induced evolution of reservoir production.
Development of the Mixing Energy Concept to Hydrate Novel Liquid Polymers for Field Injection
Authors: Kim Do Hoon , Alexis Dennis , New Peter , Jackson Adam C , Espinosa David , Isbell Taylor Jordan , Poulsen Anette , McKilligan Derek , Salman Mohamad , Malik Taimur , Thach Sophany , Dwarakanath Varadarajan 
Published: October 2018

Abstract
Polymer mixing is often challenging under offshore conditions due to space constraints. A theoretical approach is required to better understand the drivers for polymer hydration and design optimal field mixing systems. We share a novel theoretical approach to gain insights into the energy required for optimum mixing of novel liquid polymers. We present a new parameter, "Specific Mixing Energy" that is measured under both lab and field mixing conditions and can be used to scale-up laboratory mixing. We developed a simplified laboratory mixing process for novel liquid polymer that provided acceptable viscosity yield, filtration ratio (FR), and non-plugging behavior during injectivity tests in a surrogate core. A FR less than 1.5 using a 1.2 μm filter at 1 bar was considered acceptable for inverted polymer quality. We developed estimates for specific mixing energy required for lab polymer inversion to achieve these stringent FR standards and comparable viscosity yield. We then conducted yard trials with both single-stage and dual-stage mixing of the novel liquid polymer and developed correlations for specific mixing energy under dynamic conditions. Based upon the results of lab and yard trials, we tested the approach in a field injectivity test. The FR and viscosity were also correlated to a specific mixing energy to establish the desired operating window range from laboratory to field-scale applications. Such information can be used to enhance EOR applications using liquid polymers in offshore environments.