bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mature Thick Carbonate Reservoir Restimulation: Candidate Evaluation, Well Preparation, and Stimulation Strategy
Authors: Retnanto Albertus , Ryan Abraham , Amyotte Daniel 
Published: October 2015

Abstract
In mature carbonate reservoirs, the potential for bypassed or under-stimulated pays need to be addressed in order to enhance the productivity of the wells. Reservoir restimulation is one of the viable option to do this. However, due to issues with completion, perforation and other associated issues that given wells may have, restimulation should be designed and implemented such that well productivity is enhanced while simultaneously maintaining the requirements for well completion integrity. Proper design for restimulation in thick carbonate reservoirs could eliminate any negative issues that may occur during completion and prevent integrity failure during the process.
In thick carbonate reservoirs, like those found in the Middle East, the aforementioned criteria contain both petrophysical properties and current production profile obtained by production logging, establishing good foundation for implementing restimulation. Petrophysical properties help define the stimulation strategy necessary based on log potential, while the current production profile identifies the best location to stimulate over the existing completed perforated interval. In thick carbonate stimulation, uneven reservoir recovery is often observed and considerable parameters must be set during the stimulation design. Major changes to consider during the candidate evaluation for the restimulation in thick carbonate reservoir are: non-uniform pressure depletion across the formation, various pressure drawdowns, and change in PVT properties. In addition, wormholes which formed during the initial reservoir stimulation are major factor for consideration. These wormholes may act as thief zones during restimulation work and could lead to improper zonal coverage.
This paper describes restimulation design strategy which has been tailored for well preparation based on mature well conditions while also considering factors of completion and well-integrity issues. The well preparation includes focus on the reperforation selection, post-reperforation production log evaluation and production profile matching. Within the stimulation strategy, fluid selection and placement strategy will be discussed, taking into considering all aspects of a mature well.
Investigation of Stability of Hollow Glass Spheres in Fluids and Cement Slurries for Potential Field Applications in Saudi Arabia
Authors: Al-Yami Abdullah S. , Al-Awami Mohammed , Wagle Vikrant 
Published: October 2015

Abstract
Hollow glass spheres (HGS) provide an attractive method to reduce densities of drilling fluids and cement slurries for different objectives. There are several pressure ratings of HGS and selecting and testing the right type for the suitable application is important.
The objective of this paper is to evaluate performance and stability of HGS by formulating HGS based fluids in different pH conditions, formulating low density water based drilling fluids with HGS as density reducing additive, and formulating low density cement with HGS as density reducing additive
The evaluation of the stability of low-density inhibited water-based fluids formulated with HGS in diverse pH environments was for their potential application in Wasia formations in Saudi Arabia. Intensive testing of the fluids included rheological properties, pH and density measurement before hot rolling (BHR) and after hot rolling (AHR) in different pH environments at high pressure and high temperature for long time (up to 4 days).
The evaluation of the stability of low density cement utilizing HGS was for their potential to cement shallow casings in gas wells and oil wells in Saudi Arabia. In this study, we present extensive lab work that included rheology measurements, thickening time tests, free water and sedimentation tests, fluid loss test and compressive strength test.
Data generated supported the use of low density fluids formulated with HSG in Wasia Formation when applicable. Also, this study supported the use of the cement examined in shallow conditions in gas wells and oil wells. The shallow conditions simulated in the lab tests were 158ºF static temperature and 2500 psi.
Utilization of Interwell Water Tracer to Study Subsurface Flow of the Injected Water and Optimize Waterflood in Mauddud Carbonate Reservoir, Raudhatain Field, North Kuwait
Authors: Eldaoushy Ahmed S. , Al-Ajmi Moudi , Ashkanani Fatma 
Published: October 2015

Abstract
Understanding the fluid flow in the reservoir is one of the main factors affecting the success of waterflood projects. The level of reservoir heterogeneity and complexity of the structure are the main challenge factors to understand the fluid movement. Interwell water tracers is a significant approach especially in reservoirs that have high level of complexity to have better understanding of the injected water flow directions, flow units and reservoir geology.
Raudhatain-Mauddud reservoir is highly heterogeneous layered reservoir, bearing different oil qualities. The waterflood started in year 2000 and within a short period the oil rate has increased significantly but with rapid increase in the water cut. The management of Mauddud waterflood project became more complex with increasing the number of injectors and establishing injection in all layers. Interwell Tracers have been utilized to understand the complex injected water movement in the reservoir to improve waterflood management process.
Different conservative water tracers have been injected to track the injected water movement between the wells. Tracer breakthrough has been detected in many producers with wide range of tracer's residence time between the wells. Performance of tracer concentration in the stream of each well versus time has proven the flow through different flow units. The Tracer information has been utilized qualitatively and quantitatively to understand the fluid movement laterally and vertically between the flow units and provided invaluable information that has been used for optimizing Mauddud reservoir waterflood, calculating the swept volume and to optimize wells production.
This paper presents a detailed review of case history for utilizing the Interwell Water Tracer information to understand the fluid flow in the reservoir and the approach to manage Waterflood operations and optimizing wells` production.
Improved Stimulation Effectiveness of Water Injectors Using Coiled Tubing with Fluidic Oscillator-——Case Studies from a Major North Kuwait Field
Authors: Bhagavatula R.. , Al-ajmi M. F. , Rajagopalan V. S. , AL Hamad A. M. , Mofti M.. 
Published: October 2015

Abstract
Water injectors typically suffer from injectivity decline attributed to near wellbore (NWB) damage typically caused by variation in injected water quality, pores plugging caused by scale precipitation, and fines migration. Conventional stimulation treatments to improve injectivity are conducted with coiled tubing (CT) to enhance fluid placement. However, this often sacrifices stimulation effectiveness because of the relatively low fluid penetration into the formation compared to bullheading treatment. The net result is lower than the expected treatment efficiency and increased stimulation frequency.
This paper discusses a new placement technique using a fluidic oscillator (FO) tool that causes alternate bursts of fluids within the wellbore. The resulting pressure pulses propagate radially into the formation, carrying the stimulation fluid and enhancing its penetration deeper into the reservoir. A well- planned stimulation treatment recipe in combination with CT and a FO proved to be very effective in terms of stimulating water injectors.
Case histories from six water injector wells stimulated using this technique is presented. Post-stimulation results show considerable increase to injectivity rates and decrease of stimulation frequency.
Advanced ICD Application Alleviating Well Intervention Challenges
Authors: Awad Mohamed Omar , Al Ajmi Moudi F. , Safar Ahmad , Rajagopalan Vijay Sankar 
Published: October 2015

Abstract
The drilling strategy of North Kuwait has embraced in the last few years to get more reservoir contact to maximize oil recovery. Presently, the wells are drilled with high deviation angle to intersect multiple pay zones and drain the existing prospects. However, water coning and edge water breakthrough are challenging to achieve production longevity. Inflow Control Devices (ICD) is a proved tool in oil industry, which can delay the water encroachment by creating uniform drawdown across wellbore section. The production performance of ICD wells indicated stability of water cut for longer period as designed.
Answer products is the key to monitor downhole production profile to ensure the functionality of ICD units. Some reservoirs are suffering from pressure depletion and artificial lift (ESP) was installed to deepest point to increase pump efficiency. This type of completions is limiting accessibility to collect downhole data for further action.
Besides, after period if the water shutoff is required, the well intervention inside ICD completion is challenging due to bore size limitation and materials availability.
Proactive action was taken to utilize the advanced technology of ICD Completion, which allows faster execution of Rigless shutoff and reduce Rigs demands.
Challenges on Sampling and Characterization of Heavy Oil in Deep Exploratory Wells: A Field Case Study
Authors: Rajkhowa Anupam , Al-Bader Haifa , Hameed Waleed Ahmad , Al-Nabhan Abdul Razzaq , Subban Pakkirisamy 
Published: October 2015

Abstract
The objective of this paper is to present the methodology adopted to overcome challenges faced during sampling and characterization of heavy oil in deep exploratory wells.
As a part of exploration activities, two exploratory wells had been successfully drilled and tested in deeper low permeability Lower Cretaceous reservoirs. Drill Stem Test (DST) technique is adopted to test all exploratory wells for collecting production, surface and bottom-hole pressure and temperature data and collection of fluid samples for fluid characterization. As the wells are tested with retrievable packer, coiled tubing (CT) is required during activation and stimulation operations due to absence of other lifting methods. In this case study wells, coiled tubing was lowered and the well was lifted continuously with nitrogen for clean-up and to assess production behavior as there was no self-flow. Surface samples have been checked to assess contamination with diesel used for underbalance operations. Continuous nitrogen lifting helped to collect representative bottom-hole samples.
During testing, there was poor inflow of heavy oil of API 21–22 Deg, but the well could not be produced naturally in spite of repeated attempts. Matrix acid stimulation treatment was done to improve the productivity of the reservoir. Well flowed heavy oil and then gradually ceased to flow. Due to low mobility, self-flow could not be sustained. These pose significant challenges for well cleanup, flow studies and collection of representative sample for PVT analysis and fluid characterization.
Surface sampling was not favorable due to mixing with lifting nitrogen gases and only alternative method available was to collect Bottom-Hole Samples (BHS). However, proper cleanup was an issue for sampling operation. Continuous lifting with nitrogen helped to produce clean oil in both the wells. Compositional analysis was done on the nitrogen lifted sample to quantify the contamination level before lowering the down-hole sampler in order to capture representative BHS. As a result of this approach, representative samples could be captured and fluid characterization could be carried out with quality results. It has been planned to adopt the same methods in such type of situation in testing exploratory wells.
With the systematic approach representative samples could be successfully captured in both the wells where self-flow could not be sustained in spite of repeated attempts. Fluid characterization of heavy oil could be could be carried out in these two exploratory wells which are very valuable for further development planning of the reservoir / field.
Utilizing the Evolving Cement Mechanical Properties under Fatigue to Predict Cement Sheath Integrity
Authors: Shadravan Arash , Kias Evan , Lew Rolando , Maharidge Russ 
Published: October 2015

Abstract
Zonal isolation is critical for producing hydrocarbons in an economic and environmentally conscious manner. The isolation of wellbore fluids from the surrounding formation is achieved through effective cement placement. Cement is a brittle material which can fail when subjected to repeated application of stresses lesser in magnitude than the statically determined strength. In the field of mechanics of materials, repeated application of stress is referred to as fatigue loading. Well events such as hydraulic fracturing, completions or workover apply fatigue loads to the wellbore system, so it is important to understand the impact of fatigue on the mechanical behavior of the cement sheath. Many papers have investigated cement failure in wellbore systems under static load; however, few studies reviewed the effect of fatigue on cement mechanical properties. In this study, we investigated the evolution of cement elastic and strength properties under fatigue loading and evaluate the impact of the resulting changes in mechanical properties on cement sheath integrity.
A cement slurry design commonly used for wells in a US shale play was mixed and cured under downhole conditions. Three samples were failed to capture the unconfined compressive strength. Other samples from the same batch of cement were subjected to unconfined compressive fatigue cycles of 5, 20, 40 and 100 cycles respectively with a stress amplitude equal to 85 percent of the baseline unconfined compressive strength.
Axial stress and axial strain data were analyzed to determine the energy dissipated due to permanent deformation. Following fatigue loading, unconfined compressive strength and the elastic properties; Young's modulus and Poisson's ratio were measured. The cement strength, elastic properties, and dissipated energy were analyzed in reference to the number of fatigue cycles. The elastic properties determined during fatigue testing were applied to an analytical model which calculates cement stress in a multi-layer wellbore system. Results show that cement elastic properties can evolve under fatigue loading and lead to otherwise un-anticipated cement sheath failure.
Intelligent Tool to Design Fracturing, Drilling, Spacer and Cement Slurry Fluids Using Machine Learning Algorithms
Authors: Shadravan Arash , Tarrahi Mohammadali , Amani Mahmood 
Published: October 2015

Abstract
Designing drilling fluids, spacers, cement slurries and fracturing fluids are all often done by trial and error in the laboratory. In the first step, the required properties of these fluids are categorized and then efforts will be started with a rough idea of the optimum composition. This first guess usually depends on the experience of the lab analyst or fluid engineer. Afterwards, the trial and error testing starts and it continues until the fluid design gets closer to the desired fluid criteria. There are several tests data that would not be used in this method and it is hard to digest a plethora of information by user. Trial and error could be time consuming, very costly and misleading. Today, there is a need for an intelligent system which uses all the available data (Big Data), even if the data sets are not close to the desired goal, and comprehensivly offers insights for fluid designs.
This paper conducted a thorough study on the application of the machine leaning based methodologies including Artificial Neural Networks (ANN) and Gaussian Process Regression (GPR) to reduce the costs of testing, integrating available experimental data and eliminating the need for personnel supervision. These practical nonlinear regression methods empowers efficient and fast prediction tools which do not require including complex physics of the underlying system while integrating all available data from different sources. GPR which is also known as Kriging in Geostatistics literature has exceptional advantages over traditional regression methods since it does not require a known form for regression function and also has the capability of determining estimation error and confidence interval. This machine learning based tool offers comprehensive insights for intelligent fluid design and considerably reduces the cost.
Testing the Stability of Mixed CO2/N2-Foam Using New Fluorosurfactant for Enhanced Oil Recovery
Authors: Siddiqui Mohammed Abdul , Gajbhiye Rahul N. , Sultan Abdullah S. , Abu-Khamsin Sidqi 
Published: October 2015

Abstract
Foam enhanced oil recovery techniques involving super critical CO2 with surfactants are becoming popular these days due to the ability of foam to appreciably overcome problems like gravity override and viscous fingering. Foam lowers the mobility of the injected fluid consequently increasing the sweep efficiency. Several studies have been conducted to study the differences between CO2-foam and N2-foam which report that CO2 is unable to generate strong/stable foam above its supercritical point (1100 psi, 31°C) whereas N2-foam is unaffected by the increase in pressure and temperature. However, an in-depth investigation to test the stability of mixed CO2/N2–foam has not been carried out yet especially in sandstone porous media. In this work, a novel mixed CO2/N2-foam system was tested for stability for the first time in foot long sandstone cores using an amine oxide-based amphoteric fluorosurfactant.
The concentration of the surfactant solution was kept at 0.15 vol% which is above its critical micelle concentration (CMC) of 0.10 vol% that was determined through interfacial tension (IFT) measurements between sc-CO2 and surfactant solution at 1500 psi and 50°C. Foam flooding experiments were then performed at a temperature of 50°C and back-pressure of 1500 psi in which co-injection of sc-CO2, N2 and 0.15 vol% surfactant solution was carried out. N2/CO2 ratio was varied between 0-20% and in-situ foam quality was varied from 0.70 to 0.95. Each foam quality was maintained until steady state conditions prevailed. Strong foam or weak foam was characterized based on pressure drop across the core.
The results of this study show that as N2/CO2 ratio is increased from 0 to 20% an increased pressure drop across the core is observed even when the total injection rate is held constant leading to the conclusion that addition of N2 to sc-CO2 was able to generate a stronger (more viscous) foam. Average steady state pressure drop for 0.70 foam quality was 60 psi at 0% N2 and 140 psi at 20% N2 whereas for 0.80 foam quality it was 130 psi at 0% N2 and 170 psi at 20% N2. However, at 0.90 and 0.95 foam qualities average steady state pressure drop reduced to 125 psi at 0% N2 and 150 psi at 20% N2 implying that effect of N2 was most profound for 0.70 foam quality and least for 0.90 and 0.95 foam quality. Also, foam quality of 0.80 exhibits highest pressure drop with and without addition of N2. Steady state pressure drop was stable for about 0.5 PV of injection at all foam qualities indicating high foam stability with this surfactant.
This study provides a new and viable alternative for sc-CO2-foam flooding highlighting the effectiveness of addition of N2 to the foam system even at small proportions. The tested mixed CO2/N2-foam system could strengthen the potential of sc-CO2 EOR.
Steam-Foam Technology as an Option to Improve Steam Drive Efficiency
Authors: Bagheri S. R. , Clark H. P. 
Published: October 2015

Abstract
The steam-foam process is an Enhanced Oil Recovery (EOR) method which aims to improve the performance of a traditional steam drive by using a foaming surfactant. A Canadian thermal project under development in NW Alberta, which will use steam drive to recover extra heavy oil from the Bluesky Reservoir, is a good candidate for the application of steam-foam. A pilot test is planned to evaluate the benefits of the steam-foam process in this reservoir.
The steam-foam process is based on the use of a surfactant which, when co-injected with steam into the formation, generates foam. A candidate surfactant for steam-foam should be able to generate stable foam at high temperature, have a good thermal stability, a low rate of adsorption on the rock, and good solubility in brine. An experimental plan was designed to screen for appropriate surfactants to use in the field. Bulk foam height tests at high temperature, thermal degradation tests and static adsorption tests with disaggregated rock were carried out to screen the best surfactant. Two candidate surfactants were chosen based on the results. A pilot test plan was also developed for a proof-of-concept test of the candidate surfactant in the field. The primary success criterion for the test is an increase in the Bottom Hole Pressure (BHP) of the injector well after the start of surfactant injection.
Core-flooding tests are currently underway to confirm the performance of the candidate surfactant in the porous medium and determine the value of parameters required for the pilot design. The generation of strong foam in the formation should result in not only a BHP increase in the injector, but also improvement of the Steam to Oil Ratio (SOR) and ultimate recovery. The oil uplift response is dependent on the pattern geometry and geology of the reservoir and may not be observed immediately. However, the BHP increase will be immediately observed provided that strong foam has been generated near the wellbore, and this is the focus of the proof-of-concept test. A more extensive field test is planned for a later date to evaluate SOR improvement and recovery uplift.