bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on a Novel Thickened Supercritical CO2 System and its EOR Performance in Low Permeability Reservoir
Authors: Sun Xin , Dai Caili , Sun Yongpeng , Zhao Mingwei , Wang Xin , Guan Baoshan , Liu Ping , Fan Xiqun
Published: October 2018

Due to the strong mobility and energizing effect, CO2 can be injected into reservoir as a displacement agent to increase oil production in low permeability reservoir. However, low viscosity of pure supercritical CO2 (SC-CO2) resulted poor sweep efficiency. Therefore, it is essential to thicken SC-CO2 during displacement in low permeability reservoir.

In this study, a novel thickened SC-CO2 system was developed. Its viscosity with different thickener was measured by HP/HT core flooding setup. To explain the EOR mechanism, the oil saturation and sweep area in low permeability core by pure/thickened SC-CO2 flooding system was monitored through NMR on time. Furthermore, the effect of thickener concentration and flooding rate were investigated in detail, respectively.

With the HP/HT core flooding setup, the viscosity of thickened SC-CO2 system can reach to over 0.20 mPa·s while it is 0.04 mPa·s for pure SC-CO2. Increased thickener content leads to enlarged fluid viscosity within system. The increased viscosity resulted in longer breakthrough time of thickened system. After breakthrough, the continuous injection of thickened SC-CO2 system further decreases the remaining oil saturation much more obvious than that with pure SC-CO2. By analyzing the real-time distribution from T2 spectra and NMR imaging, the thickened system can involve the smaller pores which the pure SC-CO2 cannot get through. Meanwhile, thickened system can form a near piston displacement while pure system has an obvious viscous fluid advantage channel. The combination of these two processes results in higher sweep efficiency with thickened SC-CO2. Furthermore, the effect of thickener concentration and flooding rate were shown in detail. The results showed that higher thickener concentration and lower flooding rate all corresponded to higher sweep efficiency.

Due to the high injection pressure of water flooding and low sweep efficiency of pure CO2 flooding, thickened SC-CO2 flooding is proved to be a more applicable flooding agent to develop low permeability reservoir even tight oil. This study will provide new thoughts and insights mechanism about how to develop low permeability reservoir more efficiently and economically.
Enhancing Carbon Dioxide Flooding Sweep Efficiency in High Permeability Hydrocarbon Reservoirs Using Micro-Particle Gels
Authors: Fakher Sherif M. , Imqam Abdulmohsin , Bai Baojun
Published: October 2018

Carbon dioxide (CO2) flooding is one of the most applied enhanced oil recovery processes nowadays. Conformance problems such as reservoir heterogeneity can diminish the amount of hydrocarbons produced using CO2 flooding, thus resulting in a lower than expected oil recovery. This research studies the ability of a chemical conformance control agent referred to as micro-sized particle gel (PPG) to improve CO2 sweep efficiency in hydrocarbon reservoirs thus increasing oil recovery. Several core flooding experiments were conducted using a high permeability sand pack model. The factors that were examined include gel strength, varied using PPG swollen in 0.05, 0.25, 1, and 10 wt% NaCl, gel concentration using 0.5, and 2 wt% gel, presence of residual oil, and CO2 injection flow rate using flow rates of 2, 4, 6, and 8 ml/min. The ability of PPG to improve CO2 conformance was quantified using the PPG's plugging efficiency improvement. PPG with low gel strength resulted in poor CO2 conformance, but when gel strength increased above approximately 1000 Pascal, a much better CO2 conformance was observed. Higher gel concentrations resulted in an improved plugging efficiency; however, the injection of the particles took a longer time. Increasing the CO2 injection flow rate resulted in a decreased plugging efficiency. Residual oil reduced the gel strength and thus the sweep efficiency was reduced. To the authors' knowledge, no detailed core flooding experiments have been conducted to study the PPG's ability to improve CO2 conformance thus making this a very important and insightful research on the utilization of PPG during CO2 flooding. By identifying, studying and analyzing the factors that impact PPG's ability to improve CO2 conformance, novel PPG technologies can be developed and utilized in the industry to improve CO2 flooding and increase oil recovery.
Oil-Displacement Characteristics and EOR Mechanism of Amphiphilic Polymers With Two Molecular Weights
Authors: Zhang Xiangfeng , Yang Hongbin , Wang Pengxiang , Guo Shujun , Cao Changxiao , Chen Chao , Kang Wanli
Published: October 2018

Amphiphilic polymers applied in oil production are usually polymer mixtures with wide distribution in molecular weight. To determine the performance of oil displacement of polymer with specific molecular weight, it is essential to employ precipitation method to separate polymer mixtures into two molecular categories, including high molecular weight category (HM component) and low molecular weight category (LM component). The separated categories are characterized by FTIR. The rheology properties of the separated categories are evaluated by static and dynamic rheology methods. The aggregation behavior and thickening mechanism of both molecular categories is analyzed by SEM intuitively. Emulsification performances are investigated by analyzing the kinetic stability and rheological rules. Finally, displacement efficiency of the two categories is achieved by core flooding. Experimental results of CT scanning for the displaced cores and microscopic model reveal the distribution of residual oil and the mechanism of oil displacement, respectively.

The observed structural analysis indicates similar molecular structures for separated categories. However, the grafting density of the LM is higher than that of the HM. The viscosity of the LM drops more as compared to that of HM. In contrast, viscoelastic properties of LM are better than that of the HM in solutions. Emulsion particle size of HM increases at a certain degree while that of LM decreases. The stability of LM emulsion is stronger as compared to that of HM. LM is more conducive to the stability of the emulsion system owning to more hydrophobic group and better emulsion viscoelastic properties than the HM emulsion. Oil recovery efficiency of the LM reaches 54%, 5% higher than that of the HM, which indicates that the LM is more conducive to enhance oil recovery. Core flooding results suggest that the oil displacement mechanism of the HM is via mobility control, and eventually enhance the sweep efficiency; LM improves the ability of emulsifying crude oil, and thus enhance oil recovery; and synergistic effect after compounding of different molecular weight polymers showed the highest EOR effect.

Current study is of great significance for the synthesis of amphiphilic polymer and oil field applications. A polymer system with proper molecular weight distribution and grafting density can effectively improve oil recovery for a polymer flooding.
Reduced the Adsorption of Guar Based Hydraulic Fracturing Fluids in the Formation
Authors: Yin Zichen , Wang Yanling
Published: October 2018

Guar based hydraulic fracturing fluids is the most commonly utilized fracturing fluids in oil field. Whereas, it tends to lead to formation damage as a result of adsorption of guar. The adsorption behavior of guar was investigated. The approach for reducing the adsorption was explored in order to achieve the decline of formation damage and improve oil recovery. Firstly, determination method of the guar concentration was obtained via establishing the standard curve. Then, spectrophotometer was used to measure the absorbance of guar before and after adsorption on adsorbent. The obtained absorbance of guar was utilized to determine the adsorption capacity of guar on adsorbent and quantitatively demonstrate the adsorption properties of guar in the reservoir. Finally, the effect of pH, temperature, salts, alcohols and polymers was studied in order to select the condition in favor of reducing the adsorption. The linear relationship between absorbance and concentration can be detected. A simple way to determine the adsorption of guar was established: the adsorption capacity can be determined by absorbance. With increase in pH, the adsorption decreased. There was decrease in adsorption when temperature increased. Monovalent cation inorganic salt resulted in the decrease of adsorption while multivalent cationic inorganic salt and multivalent anionic inorganic salt led to the increase of adsorption. The addition of monobasic alcohol did not affect the adsorption behavior. On the contrary, the addition of ethanediol decreased the adsorption. When adding partially hydrolyzed polyacryamide (HPAM), the adsorption of guar can be decreased. Based on the above results, it can be inferred that the decline of adsorption can be achieved under the condition of high pH, high temperature, monovalent cation inorganic salt, ethanediol and HPAM. The determination approach for guar adsorption was established. The adsorption capacity was determined through the established method. The different influence factors were investigated, and the condition and method were obtained in order to decline the adsorption of guar in formation, thus reducing the formation damage.
Enhancing Plant Operability Through Control System Integration While Construction and Commissioning Phases
Authors: Farahat Abdallah , Eid Said , Abdelrazek Moustafa , Badawy Mohamed , Rostom Mohamed
Published: October 2018

Nowadays, Centralized control system becomes a key feature in designing and operating plants. It facilitates advanced control, enhance maintenance, ease troubleshooting and reduce the man power.

Agiba Petroleum Company rented a gas plant. It was constructed in western desert, Egypt to treat the production of 10 gas wells. The main facilities in this plant is separators, low temperature separator (LTS), membrane units, exchangers and compressors.

The paper presents the work done to integrate the control system of the gas plant with the units outside the plant boundaries which are launcher PLC, inlet manifold, methanol tank, well head control panel system and existing oil plant control system.

In construction phase, a field feasibility study was performed to identify the availability in Gas plant's control system, emergency shutdown, and fire and gas system. The study also includes the cables routing and the quantities of cable, glands and cable entries. It also shows the work breakdown structure (WBS), resource breakdown structure (RBS) and the schedule to perform these modifications. After performing this study, an engineering documents was issued including modified layout, cable routing, cause and effect documents and control system programing update.

This modification enhanced operations safety by give alarming and shutdown signals between the existing oil plant and gas plant, it also reduced the number of filed operators that shall monitor remote areas like the inlet manifold, launcher area and methanol tank. The paper gives an idea about workaround plans and logical engineering studies and steps that were used in critical situation to enhance the safety, promote plant operation and reduce labor.
Numerical Simulation of Gas Injection for Stable Gravity Combination Flooding After Polymer Flooding
Authors: Gao Ming , Wang Qiang , Ma Desheng , Liu Wanlu , Liu Zhaoxia , Wang Zhengbo
Published: October 2018

Remaining oil after polymer flooding is very scattered, and the remaining oil in top sections is extremely difficult to develop, yet there is no prevailing technology suitable for developing the reservoirs after polymer flooding. Gas injection for stable gravity combination flooding is studied by force analyses and numerical simulation.

The force condition of oil droplets in porous media was studied in this paper, and the action of buoyancy on oil droplets was considered during different stages of oilfield development. Based on the analyses of stress on oil, the idea of injecting gas at the top sections of the reservoir and conducting ASP flooding at the bottom sections has been proposed in this paper. Performances of different displacement modes have been predicted for the block in Daqing oil field after polymer flooding.

The research results showed that gas injection for stable gravity combination flooding had the best performance with an EOR increment of 13.53%. Comparing the remaining oil saturation of different displacement modes, the low permeability formations in the top section was effectively flooded and the remaining oil of whole formation was reduced significantly by gas injection for stable gravity combination flooding. Vertical remaining oil distribution at different time points was analyzed. Because of differential pressure in vertical direction, the remaining oil was driven to migrate downward after injecting gas in the top sections, and then the remaining oil was flooded by horizontal pressure of ASP flooding conducting at the bottom sections, thus realizing 3-dimensional flooding.

Gas injection for stable gravity combination flooding may provide a viable option for EOR after polymer flooding. The method of this paper will provide the necessary support for future applications.
Effect of Gas Adsorption on Pulse-Decay Permeability Measurements
Authors: Eliebid Mohammed , Mahmoud Mohamed , Al-Yousef Hasan Y. , Elkatatny Salaheldin , Al-Garadi Karem
Published: October 2018

Pulse-decay method is a technique used to estimate cores permeability using gas injection based on Darcy's flow model. Helium and nitrogen are generally used when the target formation is an oil formation or liquid permeability is sought. However, new approaches suggest using CH4 to avoid correcting for properties difference between the testing fluid and reservoir fluid. This study focused on the latter approach to quantify the correction to gas adsorption. The Cui et. al, model based on Langmuir adsorption isotherm is modified to Cui-Freundlich isotherm which has been proven adequate to fit the adsorption on intact reservoir rocks. The model is developed using gas and rock properties and the approach is generalized by using reduced pressure and temperature to account for the gas compressibility. The results of the modified model showed that the new model can capture effective porosity of adsorption ϕa used to correct the pulse-decay storage capacity parameters a and b. This correction in the storage volume and rock porosity values will enhance the permeability estimation in the ultra-tight rock samples.
Novel Downhole Technology With a True Point-the-Bit Rotary Steerable System Delivers Significant Operational Improvement and Cost Savings in a Challenging Reactive Shale Formation: Case Study, Kuwait
Authors: Marafi Abdulla Abdulkarim , AL Mulafy Mohamed , Sekhri Anish , Iqbal Hussan , Ebrahim Al-bateni , Farhi Nadir , Ghoneim Mohamed , Samie Mohamed , Hamida Malek Ben , Khirfan Mohamed
Published: October 2018

In pursuit of higher oil production targets in North Kuwait, a major campaign was initiated to drill reentry and new horizontal wells targeting a major multilayer carbonate reservoir. A recent study established that horizontal drilling along the northeast/southwest plane is most favorable to cut through two major unstable shale layers. Most well profiles did not satisfy this condition, given the subsurface target and the nearby wells. Contradictory to the study recommendations, multiple directional wells had to cut toward the least stress direction, complicating the tripping capability, spending many hours on back reaming to get the bottomhole assembly (BHA) out of the hole. The requirement for a reliable passive reaming device became necessary for less time-consuming trips.

This paper discusses a review of a downhole technology that has helped improve metrics against this time-reduction imperative. Multiple designs comprising additional string stabilizer(s) did not address the issues resulting from placement too far from the BHA or not having reaming capabilities. In collaboration with a specialized downhole tools supplier, the service company designed a wired rigidized heavy-duty inline stabilizer (ILS) and a bidirectional passive cutting structure compatible with the rotary steerable system (RSS) BHA requirements, replacing the existing conventional wired ILS placed within the logging while drilling (LWD) tool string. This helped the reamer device be close to the RSS to provide the necessary BHA stabilization while delivering enhanced wellbore quality through controlled reaming and back-reaming capabilities. Using this engineered stabilizer contributed to helping ensure a gauged hole by removing tortuosity, ledges, microdoglegs, and spiral patterns associated with directional drilling.

The proposed reamer device RSS BHA was successfully run on multiple wells where the shale portion became active while pulling out of the hole (POOH). The dedicated bidirectional passive reaming features above the RSS enabled reaming while drilling and back reaming the hole without any difficulties and removed obstructions more easily and efficiently. Reducing tripping time and protecting expensive BHA components from damage were a direct benefit of using these reamers. One well achieved a benchmark rate of penetration (ROP) because of a smoother running speed and weight transmission improvement. With the integration of the reamer device, the reaming process could be implemented without affecting building capability of the point the bit RSS with a build rate of more than 12°/100 ft achievable when necessary.
Improving Reservoir Heterogeneity Prediction and Well Placement by Interim Seismic Acoustic Impedance Inversion
Authors: Mahgoub Mohamed , Narino Alfredo , Badri Abdelmoneim
Published: October 2018

Improving seismic data quality prior to acoustic impedance (AI) inversion is one of the main challenges for interpreters. Proper reprocessing of seismic data may attenuate most of the noise and multiples but it can be costly and time-consuming. Therefore, while data reprocessing is in-progress, an interim solution is implemented to enhance 3D seismic quality. The solution was an effective data conditioning workflow that significantly improved seismic quality for satisfactory inversion results. Having achieved acceptable seismic data quality, we inverted the seismic volume to estimate acoustic impedance. A seismic porosity model is transformed from this acoustic impedance and used for reservoir heterogeneity prediction and well placement. The analysis indicates that the wavelet equalization is a very useful tool for stabilizing the wavelet phase and amplitude spectrum in the study area. To ensure stability of the seismic wavelet at well locations, wavelet extraction is performed before and after wavelet equalization. The structural and stratigraphic interpretation is significantly improved by inverting the conditioned seismic data to relative acoustic impedance (RAI). The acoustic impedance estimates is validated by comparing them with well log values. This validation is essential to quantify the depth conversion and to provide optimum guidelines for drilling/geo-steering. Therefore, the final acoustic impedance inversion is showed good correlation with well log data. The inversion results are successfully used to position new horizontal wells in the study area. Our experience revealed the importance of acoustic impedance inversion in guiding geo-steering wells, particularly in heterogeneous reservoirs. However, the limitation of vertical seismic resolution remains the main challenge. The study provides best practice of seismic data optimization by stabilizing wavelet phase before inversion. Ultimately this improved our ability to position horizontal wells in heterogeneous reservoirs.
Successful Applications of a Novel Compound Lost Circulation Additive with Variable Structure
Authors: Zhu Qi , Wang Yong , Zhang Yongqing , Wang Zhifa , Wang Zhaohui , Liu Chao
Published: October 2018

Lost circulation is a complicated situation in the drilling operation, wasting a lot of time and mud during processing. A serious lost circulation can cause many hazards, such as internal pressure drop, affecting normal drilling, causing well instability, inducing formation fluid into wellbore and blowout. The current plugging technology can solve some of lost circulation leakage, but there are still some problems in conventional plugging technology, such as particle size of plugging material does not match crack width, slippage of plugging material in blocking zone, and weak adhesion of plugging material additive to reservoir, which restricts the success rate of lost circulation plugging operation.

Variable structure has variable network affected by stress compound with elastic plugging material forming a plugging mixture for different leakage speed and crack width.

The rigid plugging materials with different particle sizes and different materials are mixed in a certain proportion to form a compound plugging agent for different leakage speeds and different leakage crack widths. Combined with the variable structure gel, a new type of lost circulation plugging system is used to seal the fracture-cavity reservoir leakage.

Through indoor experiment simulation, the on-site plugging formula which is suitable for fracture- vug reservoir under different temperature is formed and determined.

Scanning electron microscope shows the compound plugging mixture (CPM) has a variable network structure. Solution experiments show CPM is not diluted with water. Single plugging gel can plug 0.04-0.8 mm cracks and pressure capacity is greater than 3 MPa. With different types and sizes rigid plugging materials and elastic plugging material can block crack width of 0.15-5mm and pressure capacity is greater than 7.5MPa.

The novel CPM material has been tested and used for more than 50 wells. The porosity or micro- fracture leakage and the leakage rate of less than 30m3/h, the success rate of plugging is up to 100%, and the loss rate between 30 and 60m3/h, the success rate of plugging is beyond 85%. And the leakage rate of more than 60m3/h, the success rate of plugging is more than 80%.Leakage loss time is less than 80% shorter than conventional plugging technology.
Waterflood Management Using Streamline-Based Inter-Well Flux Information and Classical Finite Volume Reservoir Simulation
Authors: Tian Changbing , Lei Zhengdong , Zhu Zhouyuan , Chen Zhangxin , Li Lei , Wang Wenhuan , Peng Huanhuan , Tao Zhen
Published: October 2018

In this work, we implement new software for improved waterflood management by combining classical finite volume reservoir simulation together with streamline tracing and corresponding inter- well flux evaluations to optimize waterflood performance. We show reduced water cut and improved oil recovery by using streamline-based flux information to adjust well rates, while retaining the advantages of rigorous finite volume simulation.

We have introduced two basic modules here: a commercial reservoir simulator Eclipse and our own streamline tracing and waterflood management program. Waterflood simulation is performed for a certain time span until simulation is paused and the streamline tracing program is called to calculate inter-well fluxes and adjust new well rates for better waterflood performance. The simulation continues afterwards until the next tracing and adjustment point is reached. The two modules work iteratively. The streamline tracing program uses the classical Pollock's tracing method. It is designed to trace streamlines on a compressible velocity field and a general corner point grid system with non- neighboring connections. The new injection rates are adjusted according to each well's injection efficiency calculated from inter-well fluxes as proposed in previous works.

Our waterflood management program successfully works cooperatively with the commercial simulator, with data transfer realized by making the simulator to output the velocity field and other information into restart files. Streamline tracing is performed successfully not only on simple geometry corner point grid cases, but also on heavily-faulted realistic reservoirs under waterflood. Streamline- based inter-well multi-phase fluxes are calculated, in which the injection efficiencies are derived accordingly. Injectors with higher efficiencies will receive more water from the source, according to the injection allocation algorithms and vice versa. After re-adjusting injection rates multiple times during the simulation, we typically observe a reduction in field water cut of up to 5% and an increase in oil recovery in our test cases. Inter-well flux information serves as effective diagnostic tools to identify injector-producer pairs with large amount of water cycling. All simulations conducted here are rigorously finite volume based, which takes into account the full physics of non-advective processes such as gravity and capillary effects.

In conclusion, we have implemented a streamline-based waterflood management program which works iteratively and cooperatively with a commercial reservoir simulator, without switching to streamline simulation. It provides an effective solution for improving oil recovery in brown fields by combining the rigorous mathematical nature of finite volume simulation and the power of streamline- based flood management.
Multiple Scenarios Integrated Upscaling With Full Tensor Effects of Fractured Reservoirs
Authors: Tian Changbing , Lei Zhengdong , Li Junchao , Yuan Jiangru , Hao Yinquan , Zhu Zhouyuan
Published: October 2018

Heterogeneity of the fine-scale models will result in full tensor effects for the upscaled models, especially in reservoirs with channels or fractures. A flow-based upscaling approach integrating multiple flow scenarios is developed to effectively capture the full-tensor effects when upscaling from fine-scale discrete fracture models. The new approach is proposed to deliver computationally affordable simulation models under precision comparable to the high-resolution models.

The approach starts with several sets of flow-based single scenario upscaling procedures. A fine-scale discrete fracture model is built up as the reference model for all the successive procedures and comparisons. Then several flow cases (referred as scenarios) are determined according to the target simulation conditions. A global upscaling technique under multipoint flux approximation scheme is introduced to each flow scenario. An integrated output least squares method, which aims to minimize the total bias of simulation results of all the flow scenarios, is adopted to obtain the optimal transmissibility connection list of the coarse-scale models.

We design and implement several examples including two synthetic conceptual cases and a real field case. In each case, comparisons are provided for the simulation results of the proposed approach and previous upscaling approaches based on two point flux approximation schemes. The coarse-scale models upscaled by different methods are based on the same fine-scale (reference) model in each case. The results of the upscaled models are also compared to the reference model. The numerical results show that the new approach generates coarse-scale models which are closer to the fine-scale model. Although under certain conditions, traditional upscaling methods can achieve equivalent results, it is proven that the new approach is more robust when applied to more general flow scenarios. It can be noted that it may take a bit more time for the numerical simulation of coarse-scale models upscaled by the new method, due to the introduction of the non-neighbor connections. When compared to the fine- scale model, however, the improvement of computational efficiency is still pretty significant. The last case is a real field case with about 500,000 fine-scale grids and 10,000 coarse-scale grids, which demonstrates the ability of the new approach to be applied in the industry.

The novelty of the proposed approach is the optimization technique integrating multiple scenarios to generate a high precision coarse-scale model under multipoint flux approximation scheme. The new method effectively capture the anisotropic features of the coarse-scale models, which is a challenge for flow-based upscaling procedures because a single flow simulation is usually inadequate to obtain full tensor information of the upscaled models.
Development of an Operation Critical Un-Biased Composite KPI to Measure Performance of Radiation Protection Activities
Authors: Yami Mohammed H. , Farea Saeed F. , Mudaibegh Isa H. , Rehman Aziz U.
Published: October 2018

Organizations measure or monitor single KPI and present this information at various operation stage for different levels of stakeholders and business managers. This becomes significantly complex and challenging when the requirement is to monitor multiple KPIs simultaneously. Higher level decisions are required to be made as to which KPIs are the most important and correctly represent the business unit activities. This leads to oversight, if multiple factors including priority and criticality of a certain KPI is not taken into consideration, and sometimes, the selected KPI can often be a reflection of SME bias than the relevance with the business unit performance.

This article presents a risk based approach in developing an un-biased composite KPI to measure the Performance of Radiation Protection Activities. The emphasis is to derive a measurement index, which adequately reflects the performance of radiation protection activities, in accordance with their importance and criticality to operations
Wettability Alteration and Enhanced Oil Recovery Using Low Salinity Waterflooding in Limestone Rocks: A Mechanistic Study
Authors: Tetteh Joel , Janjang Nazirah Mohd , Barati Reza
Published: October 2018

Low salinity waterflooding has recently gained more attention in carbonate formations mainly due to the cost effectiveness of this improved oil recovery technique. Despite all the recent work in this area, the underlying mechanism is still controversial, making field implementation very limited.

In this work, we explore the underlying mechanism behind the low salinity waterflooding effect (LSWE) in limestone rocks by investigating the role of divalent ions. This was achieved by implementing techniques such as contact angle and IFT measurements, zeta potential measurement and coreflooding experiments tailored towards a thorough understanding of the LSWE. Seawater and low salinity brines deprived of one divalent ion were prepared while maintaining theirionic strength.

Our data shows that reducing brine ionic strength results in wettability alteration which led to improved oil recovery in limestone rocks. This observation was attributed to surface charge reduction as measured using zeta potential. The absence of Mg2+ ion in both seawater and low salinity brine resulted in surface charge polarity change from positive to negative for pure limestone/brine interface, which resulted in a significant wettability alteration as measured on contact angle from oil wet to intermediate wet for limestone surfaces. The absence of Ca2+ ions had affected both zeta potential and contact angle resulting in the least alteration in rock surface wettability. Due to the low concentration of SO42− ions in the seawater and low salinity brines, SO42- had an insignificant effect on zeta potential and coreflooding. The surface charge of aged limestone/brine systems were determined, showing the influence of oil/brine interface over limestone/brine interface in the overall crude oil/brine/rock (COBR) system. This was due to the presence of carboxylic acid present in the crude oil and indicated proper aging procedure. Divalent ions varied the interfacial tension of seawater brine/oil system potentially resulting in better mobility control due to suppressed crude oil snap-off. At low salinity, the divalents ions present in the brine was insufficient to influence the interfacial tension.

The results from the various seawater and low salinity brines concludes that low salinity waterflooding effect occurs in limestones rocks partially due to the expansion of the electrical double layer as indicated by debye length. This results in detachment of carboxylic materials from the rock surface.
Application of Quantitative Cement Evaluation Using LWD Sonic Tool in Bohai Bay of China
Authors: Liu Feng , Zhang Binqi , Zhang Lei , Han Shim Yen , Zhou Xin , Li Lin
Published: October 2018

In Bohai bay, China, more than 150 highly deviated and horizontal wells are drilled every year. For most of these wells, it is difficult to evaluate the cement quality since a conventional cement bond log (CBL) log cannot be easily performed even with drill pipe conveyance and a tractor. Therefore, the well completion operation cannot always be performed with high enough confidence. This paper describes a new quantitative cement evaluation method using logging-while-drilling (LWD) sonic tools which has been utilized successfully for several wells in Bohai bay. For these highly deviated and horizontal wells, LWD sonic tools can easily overcome the conveyance difficulty and also offer a method to evaluate the cement bond quality in the same manner as a conventional CBL. For LWD sonic tools, due to the presence of a thick steel collar, the conventional amplitude only based approach to determining bond index is insufficient to evaluate both low and high bonding (Kinoshita, 2013) and must be integrated with the attenuation rate based measurement in the form of a hybrid approach (Izuhara, 2017) to cover the full range of bonding. Additionally, the bottom-hole-assembly (BHA) design should be optimized and procedures developed to mitigate noise while running the tool, particularly with the presence of casing scrapers in the logging run, as was done in Bohai bay.

8 wells in Bohai bay have respectively used LWD sonic to evaluate the cement bonding across different oil/water zones after the cementing operation, in both 9 5/8in and 7in casings. Despite the presence of a potentially high noise source casing scraper in the BHA for all runs, the tool signal was clear enough to deliver a bond index measurement in all cases. The bond index curve derived from LWD sonic tools shows that most of these wells have good bonding for the interface between the casing and cement. According to these results the perforation program was optimized and put into practice with a solid reference. The hybrid method of determining a bond index measurement with LWD sonic tools has been deployed in the industry since 2016. The successful applications of this method in 8 wells in Bohai bay have demonstrated its feasibility and its efficiency gains where conventional evaluation methods can be challenged. This complements the theoretical development of this approach and forms solid reference for more applications in other regions cross the world.
Locally Developed Surfactants for EOR in High Temperature High Salinity Carbonate Reservoir
Authors: Hussain S. M. , Kamal Muhammad Shahzad
Published: October 2018

Surfactant injection faces a great challenge due to severe conditions in the reservoir including high salinit y and temperature which results in surfactant precipitation and/or surfactant degradation. Considering the local reservoirs conditions, a surfactant which is stable under harsh conditions, reduce residual oil saturation, and provide viscosity to the water phase is highly desirable. Most of the commercially available surfactants for EOR are anionic in nature that could have very high retention on carbonate rocks.

To overcome the challenges, a variety of gemini cationic and conventional zwitterionic surfactants were synthesized and characterized by NMR (1H and 13C), FTIR and elemental analysis. The solubility tests were conducted for all gemini cationic and conventional zwitterionic surfactants. The heat stability was investigated by putting surfactants in an oven at 90oC for 15 days followed by structural elucidation.

The characterization data exhibited excellent heat stabilities of the surfactants. The NMR (proton and carbon) and FTIR analysis of the before and after aging samples showed no major difference which indicated the excellent heat stability of the surfactants. The solubility tests revealed that the majority of the gemini cationic and conventional zwitterionic surfactant were soluble in water. Surfactants containing carbon-carbon double bond in the hydrophobic tail exhibited good solubility in water.

The tested surfactants revealed excellent solubility and found to be stable in high temperature conditions and have great potential especially in carbonate reservoirs in order to avoid adsorption issues related to anionic surfactants.
Advances in Streamlining Development Wellbore Data from Concept to Completion
Authors: Abouhenidi Malak , Tadamarry Faizuddin , Fadul Reham , Radhi Yassir
Published: October 2018

Drilling techniques have advanced significantly in recent years with the drilling of complex, multi- lateral, and extended reach wells. While drilling, wellbore geological data are collected and managed from a broad and growing range of disparate sources, presenting a need to structure and streamline these data.

A new system has been implemented to play a vital role in streamlining geological data acquisition and management. This system acts as a catalyst for reservoir characterization geologists and management to analyze the complete life cycle of development wellbores from the pre-spud/planning phase, through drilling events, daily operations, and post-drilling analysis. This system was designed with the main objective of simplifying and automating daily drilling and geosteering activities. It also extends services to unconventional resources by tracking fracking data from design phase to quality control (QC) phase.

A new data structure was introduced to support multiple sidetracks (called deepening) for a single wellbore. It eases geologists' ability to track the entire motherbore activities in one place, including multiple deepenings for each wellbore. Wellbore related data and deepening data are monitored during the building, landing, and geosteering stages until the wellbore reaches its targeted depth (TD). The data collected during the planning phase includes (but is not limited to) estimated formation tops, target zones, logs, hole sizes, etc. Daily geological observations are captured during the drilling phase. Finally, at the completion stage, the system allows geologists to compare new data (actual) against existing data (planned) using statistical and analytical tools to generate an end-of-well report with the reservoir cutoffs. In addition, based on predefined user roles, the system sends automatic notifications to the Geosteering Operations Center (GOC) and field geologists as new information is obtained.

These features, and more, provide a solid platform for making critical business decisions, and facilitate moving from passive/reactive scenarios to active/proactive production control. With this new system in place, oil and gas wellbore operations have realized the benefits of streamlining wellbore data acquisition from conception to completion to improve processes and to make better-informed business decisions.
Optimizing Onshore Well Tie-In by the Use of Thermoplastic Composite Pipe
Authors: Rodulfo Jose L. , Tavares João
Published: October 2018

Well tie-in is an activity that requires careful measurement and fabrication methods. One of the most critical spools in onshore well tie-in is the riser connecting the wing valve in the X-mas tree to the choke valve. This piping section is regularly constructed of carbon steel and rated for high temperatures and high pressures, making it expensive and difficult to manufacture. The process of measurement and fabrication can only be initiated after the rig installs the X-mas tree in order to obtain as-built measurements. In order to optimize well tie-in, Saudi Aramco installed its first two non-metallic flexible onshore risers in two oil producers.

The non-metallic flexible onshore riser is a thermoplastic composite pipe (TCP) manufactured from carbon fiber and Polyether Ether Ketone (PEEK). This construction enables it to be lightweight, strong, and able to accommodate high levels of bending strain (flexible). This TCP can be manufactured to sustain pressures of up to 15,000 psi, temperatures of up to 248 °F, and corrosion resistance to seawater, H2S and CO2. This paper describes in detail the TPC onshore riser technology design, installation and performance evaluation process.

TCP can mitigate elevation/orientation changes of wing valves and consequently accelerate tie-in procedures. The installations of these non-metallic risers were performed in under five hours each. This optimization allows for cost and time savings, as well as releasing locked potential.

This paper provides a case study of the first installations of non-metallic flexible onshore risers for well tie- in in Saudi Arabia. By comparing the conventional method of installing carbon steel sections with TCP, the reader will be able to benefit from the technology benefits analysis, lessons learned, and future applications of this technology.
An Unusual Behaviour of Fluids in Pendant Drop Measurements
Authors: Almisned Omar A.
Published: October 2018

Based on the shape and size of a formed drop of fluid introduced into another fluid (provided the two fluids are immiscible), many parameters such as Interfacial tension (IFT) are determined. In addition, investigation of the effect of a particular parameter on the IFT can be achieved by measuring the change in IFT with the variation in the parameter.

Interfacial tension, capillary forces, and wettability are the factors affecting the shape of the drop of a lighter fluid through the tip of the apparatus of the pendant drop method into a heavier fluid. Before introduced to the cell, the two phases were distinct and the contact line separating the two phases was thin and clear indicating an immiscible mixture. At constant pressure, the temperature was incrementally increased in the two-phase fluid system, and the shape of the forming pendant drop is observed and captured by a camera.

With many attempts made to form the pendant drop, the drop was never formed at specific degrees of temperature. Although the fluids had come into complete equilibrium in the laboratory before introduced to the pendant drop cell, an unusual behaviour of the two fluids has been observed. The forming and un- forming of the drop as temperature was increased has not been consistent. The two phases at some temperatures were behaving as if they were somewhat miscible. Captured pictures of the behaviour of the fluids are shown and an attempt to explain the reasons of the unusual behaviour is presented in this paper.

The unusual behaviour suggests that the IFT – temperature relationship is a complex phenomenon and confirms some inconsistencies reported in the literature. Possible reason for the strange behaviour is that although the pendant drop method is a well-established technique for measurement of the interfacial tension (IFT), it may not be applicable for all IFT measurements conditions and/or the composition of the fluids used in the system.
Enhanced Oil Recovery by Polymer Flooding: Optimizing Polymer Injectivity
Authors: Al-Shakry Badar , Shiran Behruz Shaker , Skauge Tormod , Skauge Arne
Published: October 2018

Polymer flooding has been widely applied through past decades to increase oil recovery after waterflood. Water-soluble polymers are used to increase the viscosity of injected water that is a requirement for better sweep efficiency, but accelerated production due to polymer flooding may be limited by reduced injectivity. The objective of this paper is to give guidelines for optimizing polymer injectivity as key parameter for polymer flooding design.

Analysis of polymer injection data from field tests, and different analytical and simulation approaches from academic or commercial simulators will be discussed. Field realistic laboratory flooding in porous medium has been performed. Presented experiments study the influence of pre- injection treatment like pre-shearing or other methods on rheological properties in porous medium. Injectivity is discussed in relation to polymer molecular weight, polymer concentration, pre-treatment, and presence of oil.

Field scale injectivity is reviewed from available literature data. Impact of fracturing has been analyzed in order to isolate the matrix impact on injectivity and compare to laboratory data. Investigations show that injection pressure build up in the near wellbore region, which is also referred to as polymer shear thickening behavior, limits the injectivity of polymer solutions. The effect is more significant when high molecular weight polymer is injected compared to high polymer concentration. Hence, pre-shearing the polymer solution prior injection weakens the elastic properties of polymer while maintaining its viscous properties. Also, better polymer injectivity observed when oil is present (two phase flow) in porous media compared to no oil present (one phase flow).

This paper will discuss polymer injectivity and isolate key parameters for optimizing injectivity. The data from this study gives guidelines for optimizing polymer injectivity.
Screening of Surfactants and Polymers for High Temperature High Salinity Carbonate Reservoirs
Authors: Kamal Muhammad Shahzad , Sultan Abdullah , Hussein Ibnelwaleed , Hussain S M , AlSofi Abdulkareem M.
Published: October 2018

Carbonate reservoirs typically exhibit significant heterogeneity, high temperature and high salinit ies. Surfactant and polymer selection for such reservoirs is a challenging process where extensive laboratory investigations are required to reach optimum concentration and formulation.

In this work, we have evaluated a number of anionic, cationic, nonionic, and amphoteric surfactants (total 28 surfactants) and four different polymers for high temperature and high salinity carbonate reservoirs. Surfactants used were mainly: alkyl sulfonate, olefin sulfonate, alcohol ethoxylate, carboxyl betaine, ethoxylated fluorocarbon, amine oxide-based fluorocarbon, carboxy betaine, propoxylated alcohol, linear alcohol ethoxylate, and alkyl benzene sulfonate. Surfactants were evaluated using a series of evaluation steps which include but are not limited to evaluation of compatibility, phase behavior, interfacial tension, adsorption, rheology, and core-scale performance.

Almost all anionic and cationic surfactants were either incompatible or thermally unstable. None of the anionic surfactants (sulfate, alcohol propoxylate and ethoxylate, phosphate and sulfonate), provided by various companies were thermally stable at harsh reservoir conditions. Most of the surfactants from amphoteric and nonionic classes were thermally stable and compatible at harsh reservoir conditions. Fluorinated amphoteric surfactants showed very good thermal stability at 90oC but their IFT was relative ly high (>1 mN/m). Similarly, fluorinated non-ionic surfactants showed good thermal stability but relative ly high IFT (>1 mN/m). Hydrocarbon surfactants were compatible, thermally stable and showed lower IFT values (10-2 mN/m). For core flooding experiments, fluorinated amphoteric surfactants and hydrocarbon surfactants were selected. Although fluorinated amphoteric surfactants showed relatively high IFT, they were selected due to good thermal stability, lower adsorption and synergistic viscosity enhancement with the selected polymers.

The extensive screening of surfactants and polymers for high temperature and high salinity carbonate reservoirs improved our understanding of chemical selection for such conditions. This study could be used as a guideline in future research for selection of surfactants and polymers.