bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Agents Diversion with Microseismic Monitoring – New Prospects of Refracturing for Open-Hole Horizontal Well in Tight Oil Reservoir of Junggar Basin, China
Authors: Chen Jianlin , Wang yong , Zhao Xubin , Tang Chuanyi , Gao Yan , Zhou Dan , Zeng Bin , Liu Xiangping , Li Wenhong , Wu Jinping , Li Xueyi , Li Yang
Published: October 2019

Refracturing of existing producing wells is an economical option for increasing production when compared to new drills (Urban et al., 2016; French et al., 2014). However, stage isolation during refracturing of horizontal wells can be a challenge, especially in open-hole horizontal wells. Segmentation with common mechanical tools is of high risk and costly, even ineffective sometimes. This paper presents a new tool-free refracturing technology for open-hole horizontal wells in tight oil reservoir employing chemical diverting agents and real time microseismic monitoring technology.

The implementation procedures are as follows: First, reservoir characteristics, surplus oil distribution and brittleness index are evaluated to identify the best perforation candidates for creating new fractures. Second, through the classification of predicted breakdown pressures, number of temporary plugging and diverting fracturing stages are determined. The dosage of granular and powdery plugging agents is designed. Finally, refracturing treatment are performed with an injection procedure of ‘granular plugging agents+ fracturing fluid + proppants+ powdery plugging agents + fracturing fluid’, and microseismic monitoring technology is used to help judge the effect of refracturing and adjust the refracturing operations in real time.

The refracturing treatment was performed in Well X located at Junggar Basin in western China using the method presented in this paper. The microseismic monitoring results show that multi-stage new fractures perpendicular to the horizontal well were created and a more complex fracture network was generated by refracturing in the reservoir, which verifies the validity of the tool-free refracturing of open-hole horizontal wells with chemical diversion agents. After refracturing operation, daily oil production of Well X remarkably increased from 5.1 t/d to 25.1 t/d (one year after refracturing) in the field test.

This study provides an effective tool-free refracturing technology for open-hole horizontal wells, and it was firstly applied in China. It also provides guidelines to the working engineers with respect to refracturing stimulation design and commercial viability. In addition, this technology is not only suitable for open-hole horizontal wells, but also for casing-completion horizontal wells.
New Method of Water Channeling Identification in Unconsolidated Sandstone Reservoir
Authors: GU Wenhuan
Published: October 2019

A new quantitative model of water channeling identification in unconsolidated sandstone reservoir is presented that uses the hierarchical analysis and grey correlation method as its basis for calculations. By analyzing the influential factors of water channeling, seven static factors including sedimentary micro-facies, oil viscosity, permeability, porosity, reservoir type, heterogeneity and cementation degree which impact the formation and development of water channeling are studied, and six dynamic factors including water injection index, injection/production well pressure difference, liquid production index, water cut, production/injection ratio and sand production rate which indicate the appearance of water channeling are confirmed. Used the hierarchical analysis and grey correlation method, the weights of static factors and dynamic factors are calculated, and the new identification model of water channeling is established. In the new identification model of water channeling, there are six different geological models lead to different fluid flow law in the reservoir, which is conventional zone, high permeability zone, micro- fracture in reservoir, and macro-fracture in reservoir, part-completely developed water channeling and full-completely developed water channeling. Using the new method proposed in this paper, the characteristics of water channeling in a practical reservoir group are analyzed. And the quantitative identification results are proved by tracer monitor results. The testing result of tracer is the same as the quantitative identification method, that is to say the new method is effective and accurate.
A New Approach to Measure the Wettability of Porous Media by Temperature Sensitivity of Nuclear Magnetic Resonance Relaxation Time
Authors: Kwak Hyung Tae , Gao Jun , Al-Harbi Ahmad
Published: October 2019

The wettability, specifically the wettability of the porous structure within rocks, is one of the key parameters that determine fluid flow, which determines the potential oil producibility from reservoirs. The oil wetting preference on the pore surface of reservoir rock influences the reservoir performance in various steps of oil production, such as waterflooding and enhanced oil recovery (EOR).

The surface relaxation times of nuclear magnetic resonance (NMR) are sensitive to the wettability of pore surface since they are mainly determined by the strength of fluid-rock interaction. Thus, the surface effective activation energy (ΔE), which is determined by the properties of fluid and pore surface, is the key parameter determines the NMR surface relaxation times and the wettability. Since ΔE is related to temperature by Arrhenius laws for the correlation time, the wettability of pore surface can be acquired from temperature sensitivity of NMR surface relaxation times. A new wettability measurement method for reservoir rocks has been developed based on this temperature dependence of NMR relaxation time. The proposed method is also capable of measuring the wettability of porous media under any saturation level which conventional method cannot provide. The verification of the method has been conducted with 1 sandstone and 4 carbonates rock cores.
Banyu Urip Reservoir Daily Well Deliverability Monitoring
Authors: Widyasari Stephanie Sapti , Wahyudi Hendra , Metaray Yosevina , Patel Naynesh
Published: October 2019

Banyu Urip is currently the largest carbonate oil field in Indonesia which contributes ~25% country's production target. The reservoir is producing from a combination drive mechanism with an original gas cap and a large aquifer. A dynamic production strategy is continuously implemented to achieve the production target. This paper presents an approach on reservoir surveillance strategy of Banyu Urip field in the mid-life production phase to meet production target while managing wells and facilities challenges as well as to cater to dynamic reservoir conditions. The final objectives are to understand optimum well deliverability and to do an effective reservoir monitoring and surveillance to maximize recovery.

Banyu Urip has been producing for almost 9 years so the gas oil contact is getting closer to the well perforations that is leading to gas breakthrough, confirmed by recent cased hole logging results. This condition becomes a challenge owing to facility limitation on gas processing system. In addition, there are multiple maintenance, operational and reservoir activites that lead to a variable rate throughout the day. Well limitations must be defined for each well to ensure they are operated at or below the optimal rate. In the absence of multiphase meter on each well, monthly well test data is being used to develop an equation which could relate measured flowing bottom-hole pressure (BHP) from the permanent down hole gauge to the produced rate and also to define BHP limit target on its maximum well capacity. Nodal analysis is being used to validate the equation.

The surveillance parameters are translated into a reservoir surveillance dashboard which includes maximum well deliverability, BHP limit, and real-time calculated rates. The real time data period in the dashboard could be adjusted to obtain historical data trends. This reservoir surveillance dashboard is a significant tool to ensure that all wells are at their optimum production, considering well and facility limitation. Remaining well capacity can also be calculated by comparing the measured flowing BHP vs BHP limit target. Well deliverability real time data is also effective to be used for determining well nomination to keep producing on optimum reservoir capacity when there is well maintenance/well work/high rate test activity. Producing all the wells at their optimum condition without exceeding its critical rate is one of the prudent reservoir management efforts to maximize recovery.

Operations team can use this tool as a practical guideline to monitor each well deliverability. The dashboard can also be effectively utilized in multifunctional team as a tool to manage the rate as operational needs dictate and maximize production.
Short and Long-Term Productivity Comparison of Hydraulic Fracturing Fluid Systems in East Texas Cotton Valley Formation
Authors: Al-Alwani Mustafa A. , Britt Larry K. , Dunn-Norman Shari , Alkinani Husam H. , Al-Hameedi Abo Taleb , Cedeno Miguel A. , Al-Attar Atheer M. , Al-Bazzaz Waleed H.
Published: October 2019

The aim of most hydraulic fracturing treatment is to design and implement the best stimulation strategies that help to increase the short and long-term productivity of the stimulated reservoir section. This can be achieved by selecting the best treatment fluid types that are compatible with the formation to achieve the best combination of fracture geometry and well's productivity. The main objective of this study is to investigate the short and long-term wells’ productivity for the different types of hydraulic fracturing treatment fluids in the East Texas Basin Cotton Valley formation.

Two hundred and sixty one Cotton Valley wells were identified and selected for this study. All the wells were horizontal and hydraulically fractured that were completed after 2012. The wells were classified based on the type of hydraulic fracturing fluid into four major groups: gel, water, cross-linked gel, and hybrid fracs. The hydraulic fracturing chemicals were obtained from FracFocus public record database. FracFocus data were processed then combined with production and completion data obtained from DrillingInfo database. Several data workflows were developed to classify the treatment fluid types based on the chemical ingredients of each fracturing treatment.

The productivity in this paper is reported in terms of equivalent barrel of oil which converts every 6 MCF of gas into 1 equivalent barrel of oil. This paper investigates the Cotton Valley initial production (BOE/Day), cumulative 6 months, 1 year, 2 years, and 5 years and compares the productivity for each type of hydraulic fracturing fluids. This work also provides several insights about the wells performance as a function to stimulation parameters such as the amount of pumped proppant, the volume of pumped water, and the length of the perforated horizontal lateral. The normalized production and stimulation parameters to the perforated lateral are also discussed in this paper.

This study discusses several data processing workflows that will help to illustrate the procedures to extract data from FracFocus and DrillingInfo. It provides an understanding of the hydraulic fracturing fluid types’ occurrence and measures the effect of stimulation and completion parameters on the short and long-term productivity.
A New Model to Infer Interwell Connectivity in Low Permeability Oil Field
Authors: Wang Xiang , Chen Cunliang , Han Xiaodong , He Yanfeng , Liu Xue , Lv Qichao , Dong Peng
Published: October 2019

This paper presents a new model to infer interwell connectivity in low permeability oil field. Establishing connectivity among various injectors and producers is a key to improve the understanding of a reservoir under waterflood. This understanding improves the estimates for ultimate recovery and also helps to better define the future development plan. Because of the complex pore structure, the seepage law of low permeability oilfield is more complex. Therefore, it is difficult to study the interwell connectivity.

There is a threshold pressure gradient in fluid flow in low permeability reservoirs. Therefore, the productivity formula of low permeability reservoir is deduced from the equation of motion, which is a linear model when single phase flow or water cut is stable. Similar to the capacitance–resistance model (CRM), the productivity formula and the material balance equation are combined to get the calculation model of accumulative liquid production and cumulative water injection. And the connection coefficient is solved by using the least square principle and genetic algorithm.

Different numerical simulation cases are employed to validate the derived method. The traditional method is the relationship between the instantaneous liquid production and the instantaneous water injection, and this model is the relationship between the cumulative liquid production and the cumulative water injection. In addition, the paper presents a case study to compare findings from the results of the new model and the use of interwell tracer. The results obtained from the new model shows good agreement with the results obtained from interwell tracer. The new model has been applied to nearly many wells. Compared with the single-well dynamic analysis, the accuracy of the new model is very high, but the spent time is less than half of the single-well dynamic analysis.

This method is a rapid way to have a more reliable understanding of the reservoir heterogeneity and quick prediction of reservoir performance to optimize the waterflood. The method was applied to an oil field which is effective for establishing well interaction pattern. Recommendations were given to improve waterflood efficiency.
Novel Condensate Removal with in-Situ Pressure Generation Via Thermochemical Fluids in Different Sandstone Formations
Authors: Al-Nakhli Ayman , Hassan Amjed , Mahmoud Mohamed , BaTaweel Mohammed , Al-Majed Abdulaziz
Published: October 2019

With the increasing demand on gas worldwide, condensate banking represents a challenging problem in tight reservoirs and can significantly impair the production rate. Gas injection and water-altering gas are the common techniques used to avoid the condensate development by maintaining the reservoir pressure above the dew point curve. However, these treatments are associated with high operational costs and large initial investment, also they are considered as temporary methods.

This study presents a chemical treatment for permanent removal of condensate banking using thermochemical fluids. Chemicals are injected to react downhole and generate in-situ pressure and heat. High pressure will raise the gas pressure above the dew point, and the generated heat will change the phase of liquid condensate to gas. The effectiveness of thermochemical treatment in mitigating the condensate damage in different types of sandstone rocks is presented. The effect of mineralogical composition on the condensate removal was investigated. Also, the impact of clay content on the efficiency of thermochemical treatment was investigated.

Results showed that thermochemical treatment is an effective method for removing the condensate damage from different types of sandstone formations. Condensate removal of more than 60% was achieved using Huff and Puff injection mode. Good correlation between the rock permeability and the condensate removal efficiency was observed. Higher condensate removal was obtained for the rock samples of high permeability values. Moreover, the presence of sensititve clay minerals in the treated rock showed miner correlation on the effectiveness of condensate removal, which indicates that the injected chemicals are able to stabilize the clay minerals and avoid clay damage. No clay swelling or particle migration was induced during the thermochemical treatment, since no permeability reduction was observed for all samples. Instead, the treated samples showed higher permeability values after the injection of thermochemical fluids. In addition, the profiles of condensate removal indicate that three cycles of thermochemical injection are sufficient for mitigating the condensate banking, and small condensate removal can be achieved during the late cycles of Huff and Puff operation.

This paper shows that thermo-chemical treatment can remove more than 60% of the condensate damage for different types of tight sandstones. Huff and Puff treatment was found to be very practical to remediate the condensate banking from different sandstone rocks. Also, this work confirms that thermo-chemical treatment can be applied in the formation with sensitive clays for removing the condensate banking without affecting the clay stability or inducing clay damage.
Present Day Borehole Imager Technology Conveyed While Drilling in Highly Fractured Carbonate
Authors: Murtani Anom Seto , Setiawan Andreas L. , Syarif Zilman , Pasaribu Ihsan Taufik , Siburian Pasca , Juandi Dedi
Published: October 2019

The paper will discuss the advancement of recent technology high definition resistivity imager convey with drilling assembly (Logging While Drilling) to quantify fracture geometry and secondary porosity (vuggs) in highly fractured carbonate. Oligo- Miocene carbonate Kujung formation in East Java Basin will be penetrated with high angle well and completed with Inflow Control Device (ICD) to manage water breakthrough from the presence of the fracture. High definition borehole images typically required to quantify the fracture and vuggs and locate the potential water breakthrough.

High definition resistivity images conveyed with electrical cable has been used for decades to quantify fracture geometry and vuggs. However, the well's risk such as potential stuck and mud losses will be high when the well has been depleted and has high deviation well.

Recent development technology of logging while drilling high definition resistivity images has pixel resolution 0.25". The borehole image was acquired through an array of eight buttons that has the pixel sizes to 0.25" for each button. LWD high definition imaging tool has an advantage of scanning 360 deg along the borehole's circumference without any gap along the borehole. The images acquired while drilling then processed with advance processing to quantify fracture geometry and classification of the porosity in the carbonate system for further optimization on inflow control device position and geometry.
Breakthrough in Drilling Performance Using Advanced Dynamic Modelling
Authors: Galaby Amir , Cardenas Miguel , Cengiz Ozgur , Ibrahim Sameh , Krikor Ara , Sebanne Slimane , Fedorov Artem
Published: October 2019

Downhole tool failures induced by drill string vibrations was one of the leading causes of non-productive time in a deep exploratory field in southern Iraq. To improve drilling efficiency, it was paramount to understand the primary source of potential drilling dysfunction before commencing field development phase.

To overcome the challenge, a finite element analysis (FEA) study was developed to simulate the drillstring transient dynamic behavior from bit back to surface. The model has been utilized to quantify the potential vibration, contact force, torque, displacement and other high-interest parameters of every drillstring component in the wellbore.

To fully exploit the modeling algorithms, it is required to input a comprehensive dataset including mechanical rock properties, cutting structure design, bit drive mechanism, drillstring physical characteristics, 3D well profile and expected drilling parameters. Using offset well data, surface and downhole measurements, and a thorough knowledge of drilling equipment, the model creates a virtual drilling environment simulating the downhole drilling conditions enabling the evaluation of the source of inefficiency. Finally, the model is validated for its accuracy by comparing its outcomes with actual field acquired data.

By accurately modeling the drillsting interaction with the drilling environment, the operating company was able to evaluate different BHA options to safely drill the wells and by reducing harmful vibrations, minimizing tool failures, increasing ROP, this translates to a reduction of drilling time by 24%.

This paper will share with the industry a case study demonstrating the value of the utilization of the advanced dynamic modeling which has been able to save over 500 K$ per well to the operating company by an efficient selection and placement of drill string components. This approach has enabled to outperform past drilling performance and has become the norm in similar fields in southern Iraq.
Field Implementation of Nutrient Huff and Puff in Bentayan Field, South Sumatera: Towards a Low-Cost EOR
Authors: Ariadji T. , Astuti D. I. , Priharto N. , Ananggadipa A. A. , Persada G. P. , Subiantoro E. , Erwanto P. E. , Abqory M. H.
Published: October 2019

Previous laboratory studies have shown that the combination of molasses and commercially-available fertilizer (NPK and ((NH4)2HPO4) can stimulate bacterial growth that decreases oil viscosity and interfacial tension (IFT). In this project, a huff-and-puff field implementation of MEOR nutrient injection has been conducted in two selected wells in Bentayan Field, South Sumatera, BN-38, and BN-81. The project objective is to evaluate and analyze the effect of nutrient injection towards oil recovery, changes of indigenous microbes that alter oil characteristics from the two selected wells during three months of post-nutrient injection monitoring phase. Changes of oil production were measured in-line after the gross produced liquid passes through a separator unit. The abundance of aerobic, anaerobic, and sulfate-reducing bacteria (SRB) was examined by using Total Plate Count (TPC) method, while anaerobic bacteria and SRB were cultivated using the Hungate technique. The chemical compositions of the oil were analyzed before and after nutrient injection by using gas chromatography-mass spectrometry (GC-MS) method. Fluid analysis of the oil (kinematic viscosity and interfacial tension) were measured by viscometer and IFT meter. The program of nutrient injection started with 500 bbls of first nutrient injection, followed by 100 bbls of post-flush 1, 500 bbls of second nutrient injection, 100 bbls of post flush 2, soaking for 14 days, 2000 bbls post-flush 3, and soaking for seven days. Based on the results of bacterial abundance analysis for three months, there was an increase of almost 1000-fold of total aerobic bacteria abundance and 10-fold of anaerobic bacteria abundance after nutrient injection. The expansion of bacterial abundance successfully changed the physical-chemical condition of the oil, decreasing oil viscosity by approximately 24% and IFT by 47%. In both wells, water cut values were decreased from 99% to 92%, and incremental oil was gained by 1395 barrels. Huff and puff nutrient injection seems to be low-cost EOR since it can be included in the daily operating cost with the additional cost of workforce, nutrient, monitoring, and analysis. Economic analysis calculation of this project resulted in Pay-out-Time (POT) by four months with an incremental gain of approximately 1750 barrels.
Features of O&G Supply and Demand and Trend of E&D under the Low Oil Price Cycle
Authors: Chen Yu , Lu Ying
Published: October 2019

The oil and gas supply and demand pattern, "two supply belts, three consumption centers", remains basically unchanged. However, the unconventionaloil and gas output in the United States continues to grow rapidly, resulting in an oversupply of oil and gas around the world, which has an impact on the international oil price, so there is a profound impact on global exploration and development under the background of the low oil price.

First, OPEC and Russia continued to cut supply, while the production growth of unconventional oil and gas in the United States realized its oil and gas exports, driving the change of the oil and gas geopolitical structure. Second, the global demand for crude oil grew moderately, slower than that for natural gas. Third, exploration investment plummeted under the low oil price, while newly proven reserves around the world continued to decrease. Fourth, development investment returned to low-cost and high-quality mature oil fields, while new capacity was reduced.

However, with the gradual recovery of the international oil price in the future, the global oil and gas development will show a new trend. It is expected that the upstream construction costs will rise, with onshore costs recovering faster than that of the sea areas. If the global exploration and development investment continues to decline in the future, the global oil and gas will be in short supply in the next three to five years, which will once again affect the current tight balance between oil and gas supply and demand.

Therefore, it is expected that both the oil price and the exploration and development investment will increase in 2018, and the game between OPEC and the United States will continue.
Comprehensive Approach to Assess the Productivity of Tight Zones in Contrasted Permeability Reservoirs
Authors: AlSada Abdullah , Bouaouaja Mohamed , Alyan Essam
Published: October 2019

This paper presents a generic workflow to assess direct and indirect production in reservoirs with layered contrasted permeability. The objectives are to quantify the total individual production split from those zones when compared to volumetric and evaluate the productivity efficiency.

The workflow comprehensively integrates reservoir surveillance tools such as Production Logging Tools (PLTs) to perform a zonal decline analysis through analytical approach. The numerical simulation modeling is utilized to support this assessment. The paper describes a method of capitalizing the flowmeter results and correlate them with production decline to identify the volumes swept from the tighter zones of interest.

The workflows identifies, as a result of this analysis, the split of the two portions of this swept volumes in the tight zones : a portion easy to identify, as it is produced directly through the logged wellbore or migrated vertically to most permeable zones to build-up on the attic portions of the reservoir. Such analysis when conducted in a specific field and coupled with simulation result is a powerful tool to decide on the actual mechanism affecting the sweep including the importance of gravity and percolation process. Consequently, strategic decision could be taken based on the options to develop the contrasted zones. This is including the decisions on wells configuration, whether it is more justified to fetch the tight zones volumes through vertical wells or to rationally exploiting the top layer through horizontal wells.

The workflow was applied to real case study and showed a quantitative conclusive result, it demonstrated the equilibrium, required to maintain, in the withdrawals ratio of the contrasted zones. This equilibrium will ensure to have a better sweep of lower productivity zone.
Effective Propellent Design for Mature Well Production Enhancement
Authors: Al Kalbani Mahmood , Al Saadi Hassan , Mirza Muhammad , Jumaat Shafie , Al Rasbi Said
Published: October 2019

This paper presents a field study of reperforation on three vertical oil producers wells suffering poor reservoir quality by combining deep penetration charges guns with propellent materials. Perforation charges will form the perforation tunnel and secondly the burning of the propellent material will create high gas pulse that will go through the perforating tunnels and create near wellbore fractures to overcome the near wellbore damage and improve communication with the reservoir and hence improve productivity.

Propellent simulations were carried out and results show the ability to create fractures and the estimated fracture lengths would extend beyond the wellbore damage, improving the communication between the formation and the wellbore. The propellent is in the form of sleeves installed and secured over the conventional gun carrier loaded with deep penetration charges. When the guns are detonated, the sleeve charge is ignited and instantly producing a burst of high-pressure gas which goes through perforating tunnels to generate fractures near the wellbore. The perforating job was designed with the wells on balance to enhance their productivity. The guns with propellent sleeve were successfully deployed in the wells with downhole pressure transient recorded using fast-recording pressure gauge.

After this work on Well-1, Well-2 and Well-3, several months of production monitoring of those wells show the success of the technique and demonstrate an area of applicability in such mature, low pressure reservoir suffering from near wellbore damage. The simulation of the work and how the actual gauge job data matched the simulation have been an important factor in the success in enhancing the well real performance.
Reservoir Performance Estimation for Huff & Puff CO2 Injection Using Newly-Developed Predictive Model
Authors: Setiawan Muhammad Bhakti , Syihab Zuher , Lumban Gaol Ardhi Hakim , Yasutra Amega , Rahmawati Silvya Dewi , Metra Fadhillah , Merdeka Mohammad Galang , Winata Denie Tirta , Sitompul Victor , Buhari Ari , Aziz Muhamad Choirul
Published: October 2019

CO2 Injection is one of the EOR methods that holds potential to be widely implemented. However, the underlying issues in implementing CO2 injection include the availability of CO2 sources as well as the steep capital cost associated with the surface facilities required to deliver and process the CO2. In such case, the cyclic injection, so-called Huff & Puff CO2 injection is seemingly more feasible. In this study, we propose an alternative predictive model to determine the performance of CO2 cyclic injection. This model can be utilized as a preliminary screening tool and to understand the feasibility of the operation in a quick manner. In addition, the uncertainties associated with the reservoir conditions can also be considered within the model.

Most of the efforts to develop predictive model for CO2 cyclic injection have been concentrated around empirical approach, and hence, only limited parameters are considered. In this study, we establish experimental design through reservoir simulation and perform machine learning to construct the predictive model. Therefore, most important factors driving the performance of the well underwent CO2 cyclic injection including reservoir rock and fluid properties, interaction between rocks and fluids, drainage geometry, and operating condition are incorporated. Compared to the simulation results, the proposed predictive model shows an acceptable accuracy with R-squared of above 0.95.

The result of this study can be used to help find suitable well and reservoir to be injected with cyclic CO2 injection, as preliminary analysis on the individual well performance can be conducted before performing full field simulation. The model can also be utilized to determine the optimum amount of CO2 needed, as well as the length of injection and soaking time before the well is put into production.
Acceleration Pressure Induced from Wellbore Inflow and its Influence on Productivity
Authors: Chen Zhen , Shaalan Tareq , Dogru Ali
Published: October 2019

Modelling the full physics in the wellbore is very important for investigating the wellbore pressure drop on well productivity in reservoir simulation. The pressure drop along the wellbore includes a hydrostatic, a friction and an acceleration component. The acceleration component is generally small in comparison with the overall pressure drop, and in the majority of literature it is neglected. In certain circumstance, it was shown in the literature (Ozkan, Sarica, and Haci 1999) that the acceleration pressure drop can have a significant impact on productivity in a horizontal well.

In this paper, a new formulation of acceleration pressure is derived and the results are compared with those in a commercial reservoir simulator. The new model is derived from the material balance and momentum balance equations in a coupled wellbore and reservoir system. Due to the impact of inflow from the reservoir on the velocity in the well segments, an acceleration pressure drop is induced. The physics of acceleration pressure is implemented as part of complex wellbore model in a multimillion grid reservoir simulator in a massively parallel computational environment. Detailed formulation of acceleration pressure and its derivatives with regards to primary variables are derived. Its influence on wellbore performance is shown using reservoir simulation examples. The effect of acceleration pressure is investigated using sensitivity studies of parameters such as reservoir permeability, well completion and well configuration. Simulated results show that the magnitude of impact of acceleration component on wellbore performance can be large within horizontal wells in a high-porosity high-permeability reservoir. The observations can be used for better history match and more accurate forecast.
Study on Microsphere Injections in Permeable Carbonate and Sandstone Matrix
Authors: Cao Dongqing , Han Ming , Alshehri Amar , AlSofi Abdulkareem
Published: October 2019

Significant challenges have been addressed in the application of gel-based materials for permeable carbonate matrices with multi-modal pore systems. Different from near wellbore treatments, this study focuses on a large slug microsphere injection aiming at deep fluid diversion. The objective is to demonstrate the efficiency of the microsphere injection in carbonates in comparison with that in sandstones by conducting a series of coreflooding displacement tests. Numerical simulation studies were carried out to capture response in different wettability regimes.

Coreflooding tests were conducted to study the potential of oil production that can be achieved through microspheres suspended in a polymer solution. Two sets of microsphere systems, with a median size of 0.05 and 0.3 μm in injection water, were used in this study. The tests were conducted at 95°C and 3100 psi pore pressure. The injection procedure started with waterflooding, followed by 1 pore volume of microsphere injection then post waterflooding. Effects of core mineralogy and microsphere particle size on incremental oil production were investigated. The coreflooding displacement processes including microsphere injection were simulated using UTCHEM simulator.

The effectiveness of microspheres, which are smaller than the pores/throats of the porous media, relies on the amount of microspheres injected. The coreflooding displacement with one pore volume of microsphere injection demonstrated significant incremental oil production in carbonate and sandstone core plugs, compared to polymer flooding only. The results showed that higher oil production came from higher differential pressure, which can be attributed to disjoining pressure and pore channel plugging incurred in the porous media. The microsphere injection had higher oil production in the oil-wet carbonate cores than the water-wet sandstone cores with similar permeability. It was supported by the differential pressure data that indicated that microspheres reduced the permeability in carbonates more effectively than that in sandstone cores. Moreover, microsphere injection with larger particle size yielded higher oil production. The experimental results were well matched by the fluid-flow simulator. The simulation results revealed that microsphere injection had a quick and lasting response on oil production, compared to polymer flooding. The simulation results also support our findings that the performance of the microsphere injection is more effective in oil-wet carbonates than in water-wet sandstones.

This work provides an insight of microsphere injection effectiveness in terms of achieved microsphere size, incremental oil production, rock type; and reveals the applicability and durability of such injectant in oil-wet carbonate reservoirs at harsh reservoir conditions, namely high temperature and high salinity.
Unlocking Low Resistivity Pay as New Reservoir Backbone for Mature Field Redevelopment Strategy: A Case Study of Alengka Field, Offshore North West Java
Authors: Wibowo Icuk Dwi , Prawesti Annisa , Sobani Sobani , Saputra Lulus Ilmiawan , Maulana Taufik , Luciawaty Mery
Published: October 2019

Alengka Field has been producing for more than thirty years. Like the vast majority of oil and gas field in the world, Alengka field production is on decline. Alengka Field pay reservoirs consist of more than fifteen zones which are separated in three structures. Latest infill and workover activities reveal that the major productive zones are showing watered-out and depleted reservoir pressure. The last remaining potential reservoir is a low resistivity pay zone which not fully developed yet, called as Rama and Shinta zones.

These low resistivity pay reservoirs are member of Main Formation which deposited in shallow marine depositional environment. It is characterized by 30-60 feet of pay thickness, with resistivity ranging from 1.4 ohmm up to 2.2 ohmm, with shale background resistivity up to 1.2 ohmm. It has an effective porosity up to 22% and permeability up to 10 md. The hydrocarbon existence is emphasized by the ratio of total gas reading to the background gas which more than 10 times; with peak gas up to 830 unit and poor to fair oil shows.

It is a huge contest for the offshore company to seek mature field redevelopment strategy with aging facilities to extend the economic producing life by using cost-effective and low-risk technologies. Commingle Rama and Shinta zones have demonstrated to be productive reservoirs by hydraulic fracturing. Each well can contribute 300 up to 700 BOPD of initial rate by utilizing gas lift and add 0.5 up to 0.7 MMBO of reserves. Naturally, hydraulic fracturing reservoir has rapid decline in the beginning production period which will be followed by plateau decline. The optimum fracturing parameter and gas lift performance which is combined with low angle trajectory well is identified as the essential key to improve production rate and to add maximum reserves.

Low resistivity pay zones has become the new reservoir backbone for redevelopment of Alengka field with total of 14 wells that will be drilled and 4 workover wells from 5 existing platforms that will be executed within next 3 years to add more than 7 MMBO of reserves. It will sustain Alengka field production rate more than 4000 BOPD. The recent activities consist of one infill drilling and one workover has excellent result with more than 800 BOPD in total. The successful of this campaign could open the opportunity to develop field further to the eastern part of the Alengka Field by adding new platforms and wells with total potential reserves is more than 10 MMBO. The paper will discuss about the low resistivity pay zone, production approach, recent drilling-workover results, redevelopment strategy in mature field and its challenges.
Malaysian Governance Completion Benchmarking Application towards Improving Operation Performance and Cost Efficiency
Authors: Mohd Mokhtar Shahril Ridzauddin , Omar Norjusni , Fazilah Siti Rodhiah , Bakar M. Farris , Khalid Zaidan
Published: October 2019

Between the years 2013 to 2014, the completions operations in Malaysia have shown irregular performance across all the operators and service companies. Low uptime level, exceeding budget, non-standardized design, unreasonable contingency level and excessive surplus material are among the identified elements that causes such irregular performance. The value leakage from these elements has become a huge concern to Malaysia Petroleum Management (MPM); the regulatory body of PETRONAS. A strategy was required to set up a uniform way to standardize, optimize and improve the efficiency of how completions scope is implemented in Malaysia.

Based on the analysis of over 300 wells completed from 2013 to 2015, MPM set up a 3-year roadmap on elevating the completions performance covering the pre-engineering design, operation execution, contingency computation and hardware inventory management. These elements are the basis that operators use to meet MPM Completion Minimum Standards (CMS). This CMS was set up to outline the performance benchmarking for all operators in Malaysia.

This paper will outline the strategy that MPM implemented to curb the value leakage that was effecting the completions performance. The strategy includes the establishment of an industry level collaboration known as Completions Standardization Technical Committee (COMSTEC), which comprises members from MPM, operators and service companies. This committee have jointly produced a guideline to standardize and optimize a complete end-to-end completion cycle in order to meet the performance benchmarking.

After a year of implementation, the impact of this strategy implementation was evident. The number of wells completed in 2017 that met the CMS improved by 45% compared to 2016. This optimized execution of completions scope created a value of 19% in cost efficiency throughout all the operators. Although there were challenges in the early stage of implementation, the value that all the stakeholders gained from it have exceeded the expectation and will continue to be implemented in the coming years. Astoundingly the benchmarking drives more new technologies implementation despite in low oil prices period. The relevance of both the performance benchmarking and the guideline are maintained at all times as its effectiveness is constantly monitored to reflect the latest state of the industry.
Tuberculosis Treatment Outcomes Among Prisoners And Non-prisoners In Zomba, Malawi
Authors: Singano Victor Hamilton , Kip Esther , Ching’ani Wilson , Chiwaula Lawrence
Published: October 2019

Background TB remains a major global health problem. It is particularly prevalent in prisons in sub-Saharan Africa due to overcrowding, malnutrition, high HIV prevalence and insufficient medical services. Prisoners have experienced worse treatment outcomes than the general population. We investigated the TB treatment outcomes and predictors of unsuccessful treatment outcomes among prisoners and non – prisoners.Methods We retrospectively reviewed TB registers of prisoners and non - prisoners diagnosed with TB from January 2011 to December 2016 at Zomba Maximum Central Prison and Zomba Central Hospital, Malawi. The study used routinely collected data extracted from national, standardized TB treatment monitoring tools. Successful treatment outcome was classified as the total for cured and completed treatment while unsuccessful treatment outcome was classified as the total of deaths and treatment failures. We used descriptive statistics to compare the demographics and TB treatment parameters among prisoners and non – prisoners and computed multivariate analysis to predict the independent factors of unsuccessful treatment outcomes.Results Of 1652 registered cases, 27% were prisoners (all males) and 72% were non-prisoners (58% males). The median age was 35 years (IQR: 29 - 42); 76% were Pulmonary TB cases (78% among prisoners vs 75% among non-prisoners); 83% were new TB cases (77% among prisoners vs 86% among non-prisoners); and 65% were HIV positive (50% among prisoners vs 71% among non – prisoners). Regarding treatment outcome, 1472 (89%) were cured and/or completed treatment (93% among prisoners vs 88% among non – prisoners), 2(0.2%) were treatment failures, 122 (8%) died (5% among prisoners vs 8% among non – prisoners) and 55 (3%) were not evaluated (1% among prisoners vs 4% among non – prisoners). Independent factors of unsuccessful TB treatment outcomes were noted in those with age greater than 35 years (aOR = 0.68: 95% C.I: 0.58 – 0.80), Extra-Pulmonary TB (aOR=1.69: 95% C.I: 1.08 – 2.63), HIV positive status (aOR = 0.63: 95% C.I: 0.42 – 0.94).Conclusion Good TB treatment outcomes which are comparable to the general population can be achieved among Malawian prisoners despite the challenging prison conditions.
Motivational climate, need satisfaction, self-determined motivation, and accelerometer-measured physical activity among secondary school students in China
Authors: Chen Ruzhuan , Wang Lijuan , Wang Bingnan , Zhou Yulan
Published: October 2019

Objectives Based on integration constructs from self-determination theory (SDT) and achievement goal theory (AGT), this study aims to investigate the relationship among classroom motivational climate from four perspectives (i.e., autonomy support, relatedness support, task-involving climate and ego-involving climate), three psychological needs (i.e., autonomy, competence and relatedness), self-determined motivation and physical activity (PA) in secondary physical education (PE).Methods The participants consisted of 1,186 Chinese students aged 11 to 16 years from three secondary schools around Shanghai. An accelerometer was adopted to measure moderate-to-vigorous physical activity (MVPA). Questionnaires were used to measure SDT variables (i.e., classroom motivational climate, perceived competence, autonomy, relatedness, self-determined motivation). Structural equation modelling (SEM) was used to analyze the hypothesized relationship.Results A SEM analysis revealed that autonomy support and task-involving climate were positively associated with autonomy, relatedness and competence. Relatedness support was positively related with autonomy and relatedness, whereas ego-involving climate was only associated with competence. The three psychological needs positively affected self-determined motivation, and self-determined motivation positively affected the MVPA time of secondary school students in PE lessons.Conclusion These findings support a model of motivation that integrate SDT and AGT, provides new insight into understanding MVPA in Chinese PE, and establishes a solid basis for intervention research.