bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimized Diversion System Applied in Stimulation Treatments in a Highly Naturally Fractured Carbonate Formation: Successful Case Histories
Authors: Ramirez Cristian , Campos Katya Rosa , Gonzalez Alfredo Daniel
Published: October 2018

Chemical diverter systems, such as relative permeability modifiers (RPMs), can significantly reduce effective permeability, mainly to aqueous-based fluids (e.g., acids), where the fluid enters into the interval being treated. Graded salt is a granular solid used at all temperatures that has a wide particle-size distribution (PSD) for bridging and sealing to provide effective diversion of treating fluids. This combined with an RPM fluid can help divert the entire interval during a matrix-acid stimulation. This paper discusses a review of wells treated, with excellent results, using such a chemical and bridging diversion system (CBDS) in different fields in the southern region of Mexico.

If a formation has zones containing a large number of open, natural fractures, the resulting tendency is for treatment fluids to flow into the zone(s) with the highest effective permeability or the least amount of damage instead of creating a uniform distribution over the entire interval, as is necessary. An important characteristic for a diverter product is creating a temporary skin effect during the injection of the treatment that leaves no permanent damage or that can later be removed or dissolved.

The focus of this study was on gathering more detailed information for the selection of the diverter, treatment design, and operational procedures. Additionally, the learning curve is presented associated with the challenge of stimulating a specific zone within a complex mechanical wellbore and selecting the correct candidate for applying a schedule of mechanical diversions and acid stimulations.

Laboratory study data are included to illustrate how the diverting process physically manifests, which is used to substantiate the field designs. Understanding how chemical diverters interact with the formation rock and fluid is fundamental to selecting the proper product for a specific treatment application.
Intelligent Completions First Implementation of Injector Multi-Zones – Injectivity Optimization and Efficiency for IOR Integrated Operation
Authors: Razak M. Firdaus , Khalid Aizuddin , Sapian Nik Fazril , Madzidah Asba , Samuel Orient Balbir , Khalid M. Zaidan , Mohd Shamsulbahri B. , Bakar M. Farris , Salih Mohamed Sharief , Ruvalcaba Jazael Ballina , Sadan Nur Syazana , Misron M. Al-Perdaus , Afzan A. Satar , Jamal Ajmal Faliq , A'akif Nurul Aula , Mohr Ludovic , Tajuddin Nor Baizurah , Kalidas Sanggeetha , Faizah P. Mosar , Goh Gordon , Tan Tina , Palanisamy Ravishankar , Luke Darren
Published: October 2018

The ‘B’ Field is located about 40 KM, offshore Sarawak and was discovered in 1967 with 70-80 m water depth. Structurally, ‘B’ field is charaterised by a simple relatively flat, low-relief domal anticline which is bounded to the north and south by the north-hading growth faults. The major faults are acted as effective lateral seal, which is indicated by the difference in the fluid type and fluid contacts across those faults. ‘B’ field consist of multiple hetereogenous sandstone reservoirs with permeability and porosity ranging from 25 −1700 mD and 16 −29% respectively.

‘B’ Field injectivity conformance for reservoir pressure support is very crucial as the field is undergoing severe depletions over years and unable to meet the production target. The Operator realized the importance in order to further increase the recovery factor, hence has included ‘B’ field in the Improved Oil Recovery (IOR) project to boost the production and prolong ‘B'field's life. Based on comprehensive IOR/EOR screening study, water injection process has been identified as the most amenable IOR process in ‘B'field. Hence, in Phase 1 drilling campaign, two (2) water injectors were drilled in 2016 in order to achieve the target oil recovery. Both well BWI-01 and BWI-02 were completed with Intelligent completions (IC) and expected to come online in Q4 2018.

This paper further discusses the injection strategy in ‘B’ field multi-zones to meet the zonal injectivity and reservoir zonal voidage replacement requirement for pressure maintenance over field production life. The discussion covers the reservoir characteristics and zonal injectivity challenges with surface constraints that require intelligent completions solution for IOR phase. Completions architecture and customized metallurgy needs is crucial to meet operational challenges. Fit-for-purpose and maintaning development cost is pre-requisite to achieve well injection performance for optimal production
The Triaxial Limit and Safety Factor of an Anisotropic CRA Tubular
Authors: Sathuvalli Udaya B , Suryanarayana P. V. , Rahman Shaikh , Chandrasekhar Sharat
Published: October 2018

Tubulars made with Corrosion Resistant Alloys (CRA) exhibit a moderate degree of transverse anisotropy. This results in a lower yield strength in the plane perpendicular to the rolling axis of the tubular. In addition, cold work during mill finishing introduces yield strength asymmetry along the axis.

The majority of CRA tubulars are low do/t (~ 10 to 15) production strings and their design is usually driven by pressure and tension. Given the reduced yield strength in the hoop direction (as compared to axial yield strength), a rigorous method to assess the effect of yield strength anisotropy on the triaxial limits of the pipe is needed. Though there is a substantial body of mature literature on anisotropy in metals and manufactured composites, anisotropy of tubulars has received little attention by tubular designers.

In this context, we use Hill's celebrated criterion (Hill 1950) for the yielding of anisotropic metals to develop an equation for the triaxial limits of a hollow cylinder and show that the currently used isotropic triaxial ellipse is a special case of the general limit. Also, by recognizing that purely elastic load excursions do not alter the yield surface, we extend the aforementioned triaxial limit to tubulars with tension-compression asymmetry along the tube axis. Finally, based on the notion of a strength utilization factor, we propose a method to determine the triaxial safety factor for anisotropic CRA tubulars. This method is consistent with the definition of the triaxial safety factor for isotropic tubulars.
Managing Losses with Controlled Mud Level Drilling
Authors: Smaaskjar Geir , Bergseth Einar , Hollman Landon , Arseneault Leo , Leggett Craig , Fossli Børre , Claudey Eric
Published: October 2018

Since 2016, Lundin Norway has used Enhanced Drilling's EC-Drill System to enable Controlled Mud Level (CML) drilling in the Barents Sea. The CML process allows control of the mud level in the riser in order to mitigate and manage losses while drilling, coring, tripping, cementing casing/liner, wireline operations, and well abandonment operations. With a sub-sea pump module (SPM) docked to a modified riser joint, pressure sensors on the riser and mud return line connected to the top-side, the EC-Drill equipment was able to precisely control the fluid level in the riser and manage the bottom hole pressure while drilling through potential loss zones in naturally fractured and potentially karstified carbonate formations. This paper discusses the CML system used during the project, as well as the drilling, tripping, and cementing strategy, examples of how the system was used to reduce wellbore ballooning, reduce losses during drilling, cementing and well abandonment, and several key lessons learned over the the past seven exploration and appraisal well operations.

The ability to raise and lower the riser level to manage the loss rate allowed the CML process to be used during drilling / coring operations, cementing of 7" liners and 9 5/8" casing, as well as wireline operations and well abandonment. Once the SPM and modified riser joint were deployed with the marine drilling riser and SS BOP, the system is ready for use. This allowed using the CML process in hole sections as large as 17 ½" with minimal modification of conventional drilling practices, or sacrificing ROP due to restricted flow rates. The accuracy of the riser pressure sensors on the modified riser joint allowed the system to be used while tripping to reduce surge pressures while running in hole. The system also added value during cement jobs by managing the wellbore pressure profile and return flow throughout the cement circulation and displacement. During plug and abandonment operations critical path time and cost have been reduced by managing losses to an acceptable rate during casing retrieval. The CML process has become an integral part of the operation from start to finish for Barents Sea operations for Lundin.
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

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

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

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

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

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

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

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

Well 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

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

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.
First Proppant Designed to Decrease Water Production
Authors: Green John , Dewendt Andreina , Terracina John , Abrams Benjamin , Harper Adam
Published: October 2018

This paper discusses research on how proppant selection affects fracturing treatment results in shale formations that produce high water volumes. Fracturing treatments, formation characteristics, proppant types, and post fracture treatment production results are examined in detail. A production case study that focuses on the impact of proppant selection in wells completed in formations that produce hydrocarbons with a high water cut will also be presented.

This paper analyzes laboratory tests that were performed to measure the water and oil flow rates of various commonly used proppants. A case study on how Decreased Water Flow Proppant (DWFP) performed in the Granite Wash in the Texas panhandle is also highlighted. Post fracture treatment production results are compared to traditional proppants used in direct offset wells.

Laboratory testing showed DWFP had much lower water flow and higher oil flow through the proppant pack compared to traditional proppants. The results of the laboratory tests will be used to explain and support the production case study. The field case study proves that DWFP reduced formation water production, while increasing hydrocarbon production compared to traditional proppants used in offset wells. This innovative proppant appears to decrease the relative permeability to water in the proppant pack, resulting in lower water production and higher hydrocarbon production compared to conventional proppants.

This paper introduces the first proppant specifically designed for fracturing treatments in high water cut reservoirs. A new laboratory test method of measuring water flow rate through a proppant pack was specifically developed for this type of proppant. The proppant’s wettability is introduced as a new proppant selection factor for fracturing treatments in high water cut reservoirs.
Experimental Investigation of the Effect of Pore Size on Saturation Pressure for Gas Mixtures
Authors: Salahshoor Shadi , Fahes Mashhad
Published: October 2018

Accurate determination of the dew point pressure of gas condensates in nano-porous ultra-low permeability reservoirs is crucial to prevent liquid dropout inside the formation. This paper presents a proof of concept experimental data and procedure to explain the effect of the pore size distribution on the degree and direction of the shift in the saturation pressure of gas mixtures under confinement compared to the bulk behavior.

We built a packed bed of BaTiO3 nanoparticles, providing a homogenous porous medium with pores of 5 to 50 nm, providing a volume more than 1000 times larger than typical nano channels. We designed an isochoric apparatus to monitor pressure for a fixed volume of fluid under confinement and bulk conditions simultaneously. A binary mixture of ethane-pentane undergoes an isochoric process with pressures of 10 to 1500 psi and temperatures of 290 to 425 K. The result is a set of Isochoric lines for the bulk and confined sample, plotted on the phase envelope to demonstrate the change in saturation pressure.

Many attempts in explaining the shift in saturation pressures of the reservoir fluid confined in the narrow pores of unconventional reservoirs compared to those of the bulk can be found in the literature. However, there are some contradiction between the predicted behavior using different mathematical approaches. Experimental data could be substantially helpful in both validating models and improving the understanding of the fluid behavior in these formations. Contrary to what many published models predict, our results show that confinement effects shift the dew point pressure towards higher values compared to the bulk for a fixed temperature in the retrograde region. In the non-retrograde region, however, this shift is towards lower dew point pressure values for the confined fluid compared to the bulk. Capillary condensation is assumed to be the main source of the deviations observed in the behavior of fluids inside nanopores. We evaluate published models, including those based on EOS modifications, by comparing it to experimental results to provide a quantification of their accuracy in predicting saturation pressure values for confined mixture.

This paper provides an alternative approach to examine the effect of pore size on phase behavior over a decent and practical range of pressures and temperatures. The synthesized porous medium is very helpful in uncoupling the effect of pore size from the effect of mineralogy on the observed deviations in behavior. Experimental findings are valuable for validating existing theories and can be used to adjust proposed mathematical approaches towards better predictions of saturation pressures for other systems.
Using MPD Techniques for Lower Completion Replacement: Unleashing a Powerful New Solution for Challenging Workover Interventions
Authors: Schnitzler Eduardo , Alonso Fernandes André , Savoldi Roman Roger , Pereira da Silva Paulo Henrique , Medina Ascaneo Willian , Storani de Almeida Renato , Bolfarini Harami Guilherme
Published: October 2018

This paper describes how Managed Pressure Drilling (MPD) techniques can be used in some workover and completion operations, such as the lower completion replacement. It also presents the first application of this kind of solution in a subsea well, which has been recently done in Lula field in the Brazilian pre-salt.

Highly stimulated wells in the Brazilian pre-salt carbonate reservoirs set significant challenges for well engineers when the lower completion must be replaced in workover operations. Major fluid losses are expected as the formation cannot be isolated from the wellbore. Costly loss control operations must be performed prior to the completion retrieval, introducing LCM in the well, causing formation damage and requiring further well cleaning and stimulation. A new approach was developed, in which MPD techniques such as Mud Cap Drilling (MCD) are used to cope with the fluid losses and avoid loss control operations and its associated impacts while maintaining a safe operation.

The use of two of the MPD techniques, Pressurized and Floating Mud Cap Drilling (PMCD and FMCD), in the scenario previously described allow the use of sacrifice fluid, usually treated seawater, to continuously inject underbalance or overbalance fluid into the well and avoid hydrocarbons migration during operations with highly stimulated formations still connected to the well. This also allows monitoring the well for any well control issue, as well as applying well control procedures. Even in the FMCD technique a Rotating Control Device (RCD) is used below the drilling riser slip joint to prevent any possible gas migrated into the riser to reach the rotary table.

The use of this kind of solution has turned the lower completion retrieval or replacement an operation with less deviation in terms of duration and budget. Costly loss control operations are avoided and there is no need to introduce loss control materials into the well, which could lead to problems when retrieving or installing the lower completion, such as stuck pipe or equipment failure. The customization of MPD techniques and the development of specific procedures for completion and workover with MPD have led to safe and more efficient operations in challenging subsea interventions with DP rigs.

This new approach has set an alternative workover philosophy for some pre-salt wells and also opened new opportunities worldwide by the application of this innovative solution. A significant amount of wells equipped with intelligent completion in pre-salt areas do not have a separated completion that could temporarily isolate the formation during heavy workover interventions. In this scenario the use of MPD techniques like presented in this paper might be a valuable solution.
Efficient Simulation of Two-Phase Compositional Flow in Fractured Reservoirs Using 3D Unstructured Gridding in Complex Geometries
Authors: Zidane Ali , Firoozabadi Abbas
Published: October 2018

We present a higher-order numerical model for compositional two-phase flow in fractured media in 2D and in 3D unstructured gridding. The model accommodates all types of finite elements; in particular, quadrangular and triangular elements in 2D, and hexahedra, prisms and tetrahedra elements in 3D.

We apply for the first time the fracture cross-flow equilibrium (FCFE) concept in compositional two-phase flow in 3D. FCFE is combined with the hybridized form of the mass conservative mixed finite element (MFE) and the higher-order discontinuous Galerkin (DG) method. We have developed an interface that connects computer-aided-design (CAD) software to the mesh generator. The interface enables us to generate the most complicated fracture shapes. The application is intended for fracking simulation. To the best of our knowledge the complexity of fractures that we generate/simulate is not reported in the past. Our algorithm allows flow simulation in fractures in all range of permeability values as opposed to other models where low permeable fractures affect the accuracy of the results. We demonstrate the efficiency, accuracy, and strengths of our model in comparison to alternatives including the embedded discrete fracture approach in different examples. This work covers generation and simulation of two-phase compositional flow in complex fractured media in 3D unstructured gridding.
Automating Directional Drilling: Technology Adoption Staircase Mapping Levels of Human Interaction
Authors: Wylie Robert , McClard Kevin , de Wardt John
Published: October 2018

Good directional drilling practices have a huge impact not only on drilling costs, but on improved reserves recovery, as well as on production costs such as submersible pump failures and pump rod wear. These are all helped by improving wellbore quality, lowering tortuosity, and more accurate well placement with increased percentage of the wellbore in the target zone. The very high rates of penetration being achieved today in build and hold sections require the processing and action speed of automation to supplement the directional driller’s ability to achieve these goals. In addition, there are widespread industry drives to reduce personnel at the rig site, and to automate drilling systems.

A Levels of Automation Taxonomy (LOAT) was introduced by the Drilling Systems Automation (DSA) Roadmap initiative (SPE 178841). The DSA LOAT is based on incremental automation of the four cognitive functions of interaction, which are Information Acquisition, Information Analysis, Decision Making and Action Selection, and Action Implementation. Levels of human to systems interaction are described on a nine-point scale ranging from fully manual, through levels of system support for the human, through levels of automation overseen by the human, to full automation.

Directional Drilling Automation systems are being progressively accepted by the drilling industry. This paper describes those systems’ progress along the cognitive functions and levels of automation defined by the LOAT. It highlights the usefulness of the LOAT to help users understand their current levels, provide a path forward, and manage expectations of potential users. Successful automation is neither an all or nothing proposition, but rather a progression to increasing levels of each cognitive function that balance desired goals for automation against the risks and uncertainties requiring human consideration. Best practices in wellbore placement are being adopted as automation is advanced; the value being demonstrated by automated directional drilling requires suppliers to implement and manage all necessary data flows on a consistent and reliable basis.Appropriate automation systems can improve cross-functional communications, increase organizational efficiency, and enhance geosteering involvement for timely target revisions and improved reservoir exposure.Automated Decision Making can improve consistency between individual directional drillers, wells, and of delivery of best practices developed by individual companies.Higher levels of automation require the involvement of Rig Control System builders, and increased acceptance and implementation of the automated decisions.

Automation should not be seen as an end goal in itself, but a means to add value through appropriate application. In the case of automating directional drilling, value is being added through reduced HSE impact and overall cost efficiencies such as reduced dollars per foot and reduced dollars per barrel.
Numerical Simulation of EOR from Wettability Alteration in Tight Oil Reservoir with Multiple Hydraulic Fractures
Authors: Jung Hye Young , Onishi Tsubasa , Datta-Gupta Akhil
Published: October 2018

The focus of this paper is the application of colloidal suspensions of nanoparticles, commonly known as "nanofluids" for enhanced oil recovery in tight oil reservoirs. Nanofluids are specialized colloidal solvents, compatible with various types of fluids used in oil reservoirs and they have the potential to enhance the recovery of oil and gas from a variety of rock pores (EOR). Nanofluids can be used as an important tool to alter the properties of the formations. We examine here the underlying mechanisms, including the wettability alterations and reduction of the interfacial tension driving enhanced oil recovery in tight oil reservoirs using compositional numerical simulation.

We start with a review of the nanofluid properties critical to mobilize oil in the reservoir pore network by wettability alteration. We then demonstrate the effectiveness of surfactant-based nanofluids for wettability alteration using a comprehensive chemical flooding simulation. The modeling of wettability modification depends on a shift in relative permeability and capillary pressure curves during simulation. Altered wettability affects the residual phase saturations which, in turn, influences the relative permeability and causes oil mobilization. Moreover, capillary imbibition promotes oil recovery as the wettability is altered towards water-wet conditions. We investigate the major factors in wettability modification and how they influence the oil recovery through exhaustive sensitivity studies and a Pareto-based multi-objective optimization approach.

This study concentrates on the nanofluids mechanisms in enhanced oil recovery, including the permeability alterations, rock wettability alterations and reduction of the interfacial tension. A comprehensive simulation sensitivity study and a multi-objective optimization approach are utilized to identify the dominant parameters impacting oil recovery in tight oil reservoirs using complex surfactant based nanofluids. Based on the results, a set of guidelines are suggested for selection and application of nanofluids for improving oil recovery in tight oil reservoirs stimulated with multiple hydraulic fractures.