bluuebunny/crossref_metadata_2025 huggingface dataset:
ESP Operation, Optimization, and Performance Review: ConocoPhillips China Inc. Bohai Bay Project
Authors: Jiang Zhizhuang , Zreik Bassam
Published: February 2020

SPE Gulf Coast Section Electric Submersible Pump Workshop, The Woodlands, Texas, 25–27 April, 2007

ConocoPhillips China Inc. (COPC) operates the Penglai 19–3 oil field, located offshore in Bohai Bay, the People's Republic of China. COPC holds a production sharing agreement with China National Offshore Oil Corporation(CNOOC). The Penglai 19–3 field is the second largest oil field in China with 3.8 billion bbl of oil in place, discovered in May 1999 and put on productionin December 2002.

Electrical submersible pumps (ESPs) were selected as the most economic artificial lift method to develop the field, based on the reliability, flexibility and robustness to produce wells with high flow rates and lift heavyoil in an offshore environment.

The first ESP installations were challenged with high free gas and excessives and production, resulting in operational issues and a number of failures. Even in this hostile environment, production peaked at 37,800 BOPD during November 2003, before declining as a consequence of reservoir pressure depletion. Moreover, the lower reservoir pressure increased the free gas, thereby reducing pump performance, excessive sand production lead to plugging of the pumping system and sand fill across the reservoir reduced productivity.

Various enhancements to the completion and ESP system were made during subsequent well interventions improving ESP performance, maximizing and maintaining production from the field. Furthermore, performing continuous ESP data trend analysis and performance modeling enabled the artificial lift system to be analyzed and diagnosed to maintain optimum well performance. Collaboration between Operator and Service Provider through performance review meetings and changes to operational practices were also implemented.

This paper reviews the operation, optimization, and performance of the ESP systems and the challenges faced during the first 3 years of production. Covering initial installations, subsequent well interventions, operation philosophy, optimization methodology, case studies demonstrating value of gas separation and handling devices, completion improvements, ESP configuration enhancements, run life assessment and equipment dismantle findings.
Carbon Dioxide Solvent Flooding for Increased Oil Recovery
Authors: Holm L.W.
Published: February 2020

Published in Petroleum Transactions, AIME, Volume 216, 1959, pages 225–231.

Laboratory flooding experiments on linear flow systems indicated that high oil displacement, approaching that obtained from completely miscible solvents, can be attained by injecting a small slug of carbon dioxide into a reservoir and driving it with plain or carbonated water. Data are presented in this paper which show the results of laboratory work designed to evaluate this oil recovery process, particularly at reservoir temperatures above 100F and in the pressure range of 600 to 2,600 psi. Under these conditions CO2 exists as a dense single-phase fluid.

It was found that a bank, rich in light hydrocarbons, was formed at the leading edge of the CO2 slug during floods on long cores. Formation of this bank is probably due to a selective extraction by the CO2 and, it is believed, partially accounts for the attractively high oil recoveries. In addition to the efficient displacement of oil from the pores of the rock by this process, the favorable mobility ratio related to a CO2-water flood also contributes to high oil recovery. A further advantage of this process is noted on limestone and dolomite rock, in that the CO2 reacts with the porous medium increasing its permeability.

Flooding experiments were conducted on sandstone and vugular dolomite models. The results of this experimental work show the effect on oil recovery of type of porous medium, pore geometry, flooding length, and flooding pressure. The porosity of the cores and models varied from 16 to 25 per cent and their permeabilities ranged from 100 to 200 md. A reconstituted West Texas reservoir oil, a West Texas stock tank oil, an East Texas stock tank oil and Soltrol were used to represent reservoir oils in this study. Oil recoveries ranging from 60 to 80 per cent of the original oil in place in these cores were obtained by CO2-carbonated water floods at pressures between 900 and 1,800 psi, compared with conventional solution gas drive and waterflood recoveries of 30 to 45 per cent on the same cores. Oil recoveries greater than 80 per cent resulted from floods at pressures above about 1,800 psi. These high recoveries were noted from both the sandstone and the irregular porosity carbonate cores.
Experimental Aspects of Reverse Combustion in Tar Sands
Authors: Reed Ronald L. , Reed Denzel W. , Tracht Joseph H.
Published: February 2020

Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 99–108.

Laboratory experiments on the reverse combustion of tar sands in a linear adiabatic system have shown that a highly upgraded oil can be produced from an exceedingly viscous, immobile oil.

The dependence on the air-injection rate of peak temperature, combustion-zone velocity, oil recovery, air-oil ratio, residual coke and oil, fuel burned and distribution of product gases is shown graphically. Effects of initial temperature, oxygen concentration, oil saturation and heat loss are discussed. Experiments bearing on the coking properties of heavy oils are mentioned and some results exhibited.

Field application of the process hinges on the existence of adequate air permeability and the rate of reaction under reservoir conditions.

Introduction

It has been established that oil can be recovered from underground reservoirs by means of at least two fundamentally distinct methods involving in situ combustion of a certain fraction of the oil. Characteristic of both of these known methods is the production of oil from one or more wells by means of hot gases formed when a high-temperature reaction zone is advanced through the reservoir. In both cases, the reaction zone is created by heating certain of the wells to a sufficiently high temperature prior to the introduction of air, and the zone is maintained and advanced through the reservoir by appropriate control of the air-injection rate.

In the first of these methods, which is called "forward combustion", the combustion zone advances in a direction which is generally the same as that of the air flow; whereas in the second method, "reverse combustion", the combustion zone moves in a direction generally opposite to that of the air flow.

Forward combustion, on the one hand, is an ideal combustion process in the sense that a minimum of the most undesirable fraction of the oil is consumed as fuel in the form of coke, a clean sand is left behind and generated heat is used as efficiently as possible. However, the applicability of forward combustion is limited. Since the products of combustion, vaporized oil and connate water must flow into relatively cold regions of the reservoir, there is an upper limit on the viscosity of oil which can be moved by this process in a practical and economical fashion.
Theoretical Considerations of Reverse Combustion in Tar Sands
Authors: Warren Joseph E. , Reed Ronald L. , Price Harvey S.
Published: February 2020

Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 109–123.

The behavior of the reverse-combustion process in a linear adiabatic system is theoretically investigated by means of an idealized physical model. This model is described by a pair of non-linear equations involving heat and mass transfer which are coupled by a concentration-dependent reaction-rate function of the Arrhenius type.

The differential equations governing the quasi steady-state temperature and concentration distributions are approximately solved by using either physical or mathematical simplifications. It is shown that the reverse-combustion process can be mechanistically described by simple physical models whose behavior equations can be solved formally. It is further demonstrated that the derived reverse-combustion equations can be solved numerically within the error limits for the experimental data. The theoretically predicted peak temperature-flux-velocity relationship exhibits reasonable agreement with experimental data obtained from Athabasca tar sand.

The principal contribution of this work lies in its usefulness as a starting point for developing a more comprehensive theory. A description of the vaporization-coking process must be obtained; then, the theory must be extended to three dimensions to include geometrical effects and heat losses.

Introduction

In another paper, the physical processes visualized as occurring during reverse combustion have been described. In this paper, the extent to which an elementary theory can account for experimental observations is determined. Theoretical results that can be used to estimate some of the behavior characteristics of importance to this process are also presented.

Since it is not possible to include all the features of the combustion mechanism of which we are currently aware, the mathematical formulation refers to the highly idealized system developed herein. This simplified physical model is based on the simultaneous transfer of mass and heat accompanied by a chemical reaction; it is described mathematically by a pair of coupled, nonlinear differential equations. Similar sets of equations have been studied extensively in the field of flame propagation; an excellent review of these investigations has been published by Evans.
Miscible Displacement - Flow Behavior and Phase Relationships for a Partially Depleted Reservoir
Authors: Wilson J.F.
Published: February 2020

Published in Petroleum Transactions, AIME, Vol. 219, 1960, pages 223–228.

An experimental investigation has been made of gas-driven slug displacements in a system of high gas saturation to evaluate the process for use in a California reservoir. Fluid compositions, temperature, pressure and core permeability duplicated reservoir conditions as closely as possible. The temperature was above the critical of the slug materials. The slug composition required for 100 per cent oil recovery in the linear flow systems was found to agree with that determined from equilibrium phase studies.

A qualitative theory for the slug displacement of two-phase systems is proposed and found to be in general agreement with the observed flow behavior. The theory predicts that the length of the reservoir fluid slug transition zone will increase with increased initial gas saturation and decrease with increased oil swelling accompanying the composition change from reservoir oil to the critical composition.

The precipitation of small amounts of an asphaltic phase during the formation of the transition zone had no adverse effects on the Yow behavior of otherwise miscible systems.

Introduction

Despite the large number of recent publications relating to oil recovery by miscible displacement, little information is available concerning the behavior of crude oil-natural gas systems at conditions likely to be encountered in field application. The laboratory data reported here were obtained during an investigation of the possibility of using a gas-driven LPG slug in a partially depleted California reservoir. Seven gas-driven slug displacements employing slugs of different compositions and sizes were made in 26- to 27-ft long sandstone cores. The equilibrium phase behavior of the systems was also determined.
Displacement of Oil by Rich-Gas Banks
Authors: Arnold C.W. , Stone H.L. , Luffel D.L.
Published: February 2020

Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 305–312.

The purpose of this research is to determinethe efficiency of small banks of enriched gas driven by methane in displacing oil from a porous medium andthe effects of variation in bank size and composition of that efficiency.

Most of the experiments were conducted in a sand-packed tube 20-ft long and 1/2-in. in diameter. The hydrocarbon system generally used was methane, butane and decane at 2,500 psia and 160°F.

The results of these experiments indicate that, in the regions contacted by the gas, a small bank of an oil-miscible gas driven by methane can displace all of the oil in a piston-like manner. If the enriched gas is of such composition as to remain immiscible with the oil, displacement of oil is less efficient than for the miscible case, and the gas hank travels through the sand with a velocity less than that of the driving gas.

These data along with theories discussed imply that smaller banks and less total gas are required when the enriched gas and oil are miscible.

Introduction

Widespread application of enriched-gas drive to the recovery of oil rests upon a key factor the use of limited quantities, or "banks", of enriched gas. At the present time, the value of liquefied petroleum gas or other enriching agents discourages their use in a continuous injection technique, or even in a large bank, except in a few isolated reservoirs. If small banks of enriched gas driven by methane were as effective in displacing oil as is continuous injection, the enriched-gas drive process might be applied to a larger number of reservoirs.

Previous research on the mechanics of the enriched-gas drive process reported by Stone and Crump and by Kehn, Pyndus and Gaskel has utilized continuous injection of enriched gas. This work has shown that two types of displacements occur. With gases containing sufficient intermediates, the oil is displaced miscibly and complete recovery is obtained from the regions swept. When gases are used which contain insufficient intermediate hydrocarbon for miscible displacement, oil is displaced immiscibly. In the latter type, selective solution of the intermediate hydrocarbons causes a swelling and reduction in viscosity of the oil and leads to an increased recovery over that obtained by dry-gas (methane) drive.
The Efficiency of Miscible Displacement as a Function of Mobility Ratio
Authors: Habermann B.
Published: February 2020

Published in Petroleum Transactions, AIME, Vol. 219, 1960, pages 264–272. Paper presented at 35th Annual Fall Meeting of SPE, Oct. 2–5, 1960 in Denver, and at the California Regional Fall Meeting of SPE, Oct. 20–21, 1960 in Pasadena, Calif.

Artificially consolidated sand models, representing one-quarter of a five-spot, have been developed and used to study factors affecting miscible displacement. Sweep efficiency at breakthrough, size of the mixing zone between two miscible liquids and per cent are contacted by drive after breakthrough were determined for the high mobility ratios encountered in actual reservoirs. Quantitative relationships between the degree of viscous fingering and mobility ratio were obtained by measuring the length of the fluid interface.

Scaled miscible-slug experiments, supported by field evidence reported in the literature, have shown that when the slug is followed by dry gas the process is less efficient than expected. In addition to low areal sweep efficiencies encountered for high mobility ratio displacements, the effectiveness of a miscible slug is greatly reduced. This is caused by an accelerated growth of the mixing zone between the driving and the displacing fluids.

Introduction

Considerable interest in miscible displacement as a secondary recovery process has been shown by the oil industry in recent years. In addition to extensive laboratory investigations, numerous field operations have been initiated so that 39 miscible displacement projects had been reported in the United States by early 1959. By far the most popular approach in these projects is the use of an LPG slug followed by dry gas.
Multiscale Modeling of Gas Transport in Shale Matrix: An Integrated Study of Molecular Dynamics and Rigid-Pore-Network Model
Authors: Wang Sen , Feng Qihong , Javadpour Farzam , Zha Ming , Cui Ronghao
Published: February 2020

The physics of gas transport through shale systems remains ambiguous. Although several theoretical and experimental studies have been reported, most concentrate only on the permeability of shale kerogen. Shales, however, are composed of various proportions of organic matter and inorganic minerals (e.g., calcite and clay). Inorganic pores are larger than organic pores, thus affecting apparent permeability. To accurately predict the apparent permeability of shale, we couple molecular dynamics (MD) and a pore-network model (PNM) to develop a multiscale framework for gas flow through shales. First, we use nonequilibrium MD (NEMD) to study the pressure-driven flow behavior of methane (CH4) through organic, calcite, and clay [montmorillonite (MMT)] nanopores under reservoir conditions, from which, using the slip-corrected Poiseuille equation, we propose a mass-transport model accounting for the contributions of both the adsorbed-phase fluid and bulk fluid. Then, we incorporate these formulations into a shale PNM in which the influences of shale composition and bimodal pore-size distribution (PSD) are taken into account. We also develop an analytical model for the apparent permeability of shale matrix using the bundle-of-capillaries approach. In comparison with previous methods, our proposed models highlight the effect of relatively greater pore sizes in inorganic matrices. This work provides an efficient tool for better understanding gas transport through shale systems at both molecular and pore scales.
Using Machine Learning Methods To Identify Coal Pay Zones from Drilling and Logging-While-Drilling (LWD) Data
Authors: Zhong Ruizhi , Johnson Raymond L. , Chen Zhongwei
Published: February 2020

Accurate coal identification is critical in coal seam gas (CSG) (also known as coalbed methane or CBM) developments because it determines well completion design and directly affects gas production. Density logging using radioactive source tools is the primary tool for coal identification, adding well trips to condition the hole and additional well costs for logging runs. In this paper, machine learning methods are applied to identify coals from drilling and logging-while-drilling (LWD) data to reduce overall well costs. Machine learning algorithms include logistic regression (LR), support vector machine (SVM), artificial neural network (ANN), random forest (RF), and extreme gradient boosting (XGBoost). The precision, recall, and F1 score are used as evaluation metrics. Because coal identification is an imbalanced data problem, the performance on the minority class (i.e., coals) is limited. To enhance the performance on coal prediction, two data manipulation techniques [naive random oversampling (NROS) technique and synthetic minority oversampling technique (SMOTE)] are separately coupled with machine learning algorithms.

Case studies are performed with data from six wells in the Surat Basin, Australia. For the first set of experiments (single-well experiments), both the training data and test data are in the same well. The machine learning methods can identify coal pay zones for sections with poor or missing logs. It is found that rate of penetration (ROP) is the most important feature. The second set of experiments (multiple-well experiments) uses the training data from multiple nearby wells, which can predict coal pay zones in a new well. The most important feature is gamma ray. After placing slotted casings, all wells have coal identification rates greater than 90%, and three wells have coal identification rates greater than 99%. This indicates that machine learning methods (either XGBoost or ANN/RF with NROS/SMOTE) can be an effective way to identify coal pay zones and reduce coring or logging costs in CSG developments.
The Reduction of Pressure Gradients in Oil Pipelines by the Addition of Water: Numerical Analysis of Stratified Flow
Authors: Charles M.E. , Redberger P.J.
Published: February 2020

This paper was presented at the AIChE - SPE Joint Symposium on Multiphase Flow in the Production and Drilling of Oil Wells, September 25–28, 1960, in Tulsa, Oklahoma

The addition of water to crude oil pipelines appears to be an important method for decreasing the pressure gradient for a given oil throughput. Although the concentric oil-in-water flow pattern provides the greatest possible reduction, the general case, in which the liquids are stratified as a result of the oil and water having different densities, is also characterized by reductions in pressure gradient.

To evaluate the magnitude of the pressure gradient reduction to be expected in stratified flow systems, the Navier-Stokes equations were solved by a numerical procedure utilizing a digital computer, for the laminar stratified flow of two Newtonian liquids - oil and water - in a circular pipe. Liquid flow rates were obtained for the flow of five hypothetical oils ranging in viscosity from 4 to 1500 centipoises in the presence of water, by computing the oil and water velocity profiles for a series of arbitrary oil-water interface positions. It was found that the maximum values for the pressure gradient reduction factor ranged from 1.12 to 1.31 for the five oils and occurred at water contents ranging from 12 to 93 per cent respectively.

The computed reduction factors were considerably lower than experimental values and this appears to indicate that wave motion and mixing at the oil-water interface produces a further and very significant reduction in the pressure gradient.
Cement Plug for Water Shut-Off Using Coiled Tubing Hydrostatic Valve: Case Studies
Authors: Mehmood Azfar , Sattar Abdul , Akbar Nabeel , Temuri Saqib Jah , Fazal Adnan , Saeed Salman , Khokhar Saad Yousuf , Yousuf Arif , Rehman Aziz ur , Dar Afnan Ahmed
Published: February 2020

Accurate fluid placement had always been a challenge in depleted reservoirs. Criticality of such jobs multiplies when cement plug is to be placed in a depleted reservoir or when there is a marginal tolerance in terms of volume or differential pressures for the placement of cement plug. Various techniques are used in industry to spot specific cement slurry volume in stages to get accuracy in plug depth. Bailers being most successful, demerits from having very less volume of cement slurry which can be placed, resulting in multiple runs. To effectively place fix quantity of chemical plug or cement slurry in a well, a coiled tubing conveyed hydrostatic valve (fluid retainer) can be successfully deployed, by placing known quantity of liquid only.

In depleted oil and gas wells (especially the ones in secondary recovery phase) there is a static sump present. Reservoir shut off solutions cannot be used in this scenario as the increase in hydrostatic head causes loss of the pill into the the reservoir zone. In such scenarios, cement plugs are preferred to be dumped using dump bailer, however, for volumes larger than 1 bbl bailer option is not feasible. Hydraulics balance is crucial to job success, and such applications virtues the use of a coiled tubing conveyed Hydrostatic Valve.

This paper discusses operation of hydrostatic valve and present case studies of two wells in Pakistan, where this technology is effectually implemented together with acid soluble and salt saturated cement slurry.
An Experimental Evaluation of Thermochemical Fracturing in Layered Formations
Authors: Tariq Zeeshan , Mahmoud Mohamed , Abdulraheem Abdulazeez , Al-Shehri Dhafer , Al-Nakhli Ayman , Asad Abdul
Published: February 2020

Current global energy demand and supply gap needs the best engineering methods to recover hydrocarbons from the unconventional hydrocarbon resources. Unconventional resources mostly found in highly stressed, over pressured, and deep formations, where the rock strength and integrity both are very high. The pressure at which the rock fractures or simply the breakdown pressure is directly correlated with the rock tensile strength and the stresses acting on them from the surrounding formations. When fracturing these kinds of rocks, the hydraulic fracturing operation becomes much more challenging and difficult, and in some scenarios reached to the maximum pumping capacity limits. This reduces the operational gap to optimally placed hydraulic fractures.

In the present research study, a novel thermochemical fracturing approach is presented to reduce the breakdown pressure of the high-strength layered formations. The new approach not only reduces the breakdown pressure of the layered rocks but also generate highly conductive fractures which can penetrate in most of the layers being subjected to fracturing. The hydraulic fracturing experiments presented in this study are carried out on four layered cement block samples. The composition of cement blocks is synthesized in this way that it simulates the real rocks.

The results showed that the newly proposed thermochemical fracturing approach reduced the breakdown pressure in layered rocks from 1495 psia (reference breakdown pressure recorded from conventional hydraulic fracturing technique) to 1107 psia. The post treatment experimental analysis showed that the thermochemical fracturing approach resulted in deep and long fractures, passing through majority of the layers while conventional hydraulic fracturing resulted in a thin fracture affected only the top layer. Thermochemical fluids injection caused the creation of microfractures, improved the porosity and permeability, and reduces the Young's modulus of the rocks. The new technique is cost effective, non-toxic, and sustainable in terms of no environmental hazards.
Uplifting the Profitability of a Mature Gas Giant in Pakistan Using Diminutive Sidetracks
Authors: Bugti Jahanzeb Ali , Ahmed Sheraz
Published: February 2020

One of the key challenges for Oil and Gas industry in current (low price) scenario, is efficient handling of mature Assets. This is because of the fact that reasonable amount of hydrocarbons still exist in such reservoirs but in scattered and partially-drained locations. Moreover, lower production rates, combined with ever-increasing costs, hardly satisfies the economic screening criteria for their expansion with new wells. This study presents an approach used on such a Mature Gas Giant in Pakistan, in order to re-vitalize old wells and exploit the scattered sweet spots (still prevailing in reservoir), with the help of a robust engineering and geological strategy.

The field under study was discovered in 1950s, in the eastern onshore area of Pakistan. The primary reservoir, under study, is a depletion drive fractured limestone i.e. no pressure support was observed in P/Z data. At present, more than 92% of the EUR has already been produced from this reservoir, which translates to 82% of Field In-Place volume. However, the performances of multiple wells have gone down with time, due to the depletion in Reservoir Pressure and the channeling of water towards producing wells-through the faulted/fractured zone. To cut water production and arrest the Annual field decline of 7-8 %, various activities have been carried out, including cementing, tubing size reductions, chemicals; but all the efforts went in vain.

In this paper, a detailed approach is presented, that was taken to tap the undrained areas in the vicinity of the existing producers - suffering from water hold ups and low gas rate problems. The Production logs were used first to identify the water production zone. Afterwards, a comprehensive algorithm was developed to analyze the Geological and Geophysical parameters and identify the undrained prospects while keeping minimal capital exposure. So far, a gain of around 10 MMScfd have been observed with the help of two engineered Sidetracks - which has added around 10 - 15 BCF reserves in our portfolio.

The most common issues encountered in a mature asset are liquid loading and water breakthrough. This study illustrates the methodology to resolve such issues with minimum investment towards the end of field life. It focuses on the benefits of sidetracks as a production enhancement tool, to reduce the annual decline. This paper offers an innovative approach, to utilize each geological and engineering data set in a systematic manner, in order to re-work old wells at optimum locations to evade issues affiliated with gas entrapment and water production. In the end, the paper also describes the evaluation process of production gains, geology, well construction, and completion types, that can be adapted to reap maximum rewards in such mature fields.
Experimental Investigation of Newly Synthesized Gemini Surfactants as Shale Inhibitors in Drilling Fluids
Authors: Murtaza Mobeen , Kamal Muhammad Shahzad , Hussain Syed Muhammad , Mahmoud Mohamed
Published: February 2020

Environmental concerns and the economic aspects curtail usage of oil-based drilling fluids (OBDF) during the drilling operations through shale formations. The OBDF is highly effective in controlling the swelling potential of the clay-rich shale formations in oil/gas wells. Hydration of shale formation by water-based drilling fluids (WBDF) leads to several problems such as collapse of boreholes, tight holes and stuck pipe which may preclude further drilling and time loss in rectifying the problems, leading to heavy economic losses. Designing the drilling fluid that reduces the interaction with shale, is important for safe and efficient drilling. This study investigates the new gemini surfactants as shale swelling inhibitors in the field of drilling.

To assess the performance of new cationic Gemini surfactants two reliable clay sources were considered. The first clay (Kaolinite) is from an unconventional formation and the second is sodium bentonite. The inhibition characteristics of gemini surfactants were tested using a dynamic swelling tester.

Different formulations based on commercially available solutions for shale swelling inhibitors were applied and compared with cationic shale inhibitor. It was observed that the new gemini surfactants reduced the shale swelling by different percentages for various gemini surfactants based on their spacer length. It also showed acceptable performance compare with common shale inhibitors used in the industry.
Employing Innovative Distributed Temperature Sensing Technique for Conclusive Downhole Leak Detection via Coiled Tubing: A Case Study from Pakistan
Authors: Khalid Aizaz , Briones Victor , Ramondenc Pierre , Mhiri Adnene , Khan Rao Shafin , Molero Nestor , Kamran Muhammad , Ali Syed Dost , Rashid Kamran , Mallah Sohail Ahmed
Published: February 2020

Leak identification across well completions is a crucial operation in the oil and gas industry. A failure of well barriers can result in uncontrolled release of hydrocarbons and pose major risks to personnel and environment. Downhole gauges are widely used to provide pinpoint measurements of pressure and temperature across the completion; however, those measurements alone are insufficient to properly diagnose single or multiple well integrity issues. Alternative well intervention methods are needed to qualitatively estimate the location and number of potential leaks.

For the past decade, distributed temperature sensing (DTS) has been used in wellbore completions and surface pipelines with preinstalled fiber optic lines to identify leaks by monitoring and processing temperature profiles across the length of the installation. The proposed methodology makes use of a similar principle, relying on coiled tubing (CT) to deploy the fiber optics and conduct DTS integrity assessment in wells completed without fiber optic lines. This use of fiber optics inside a CT pipe also provides simultaneous real-time downhole measurements, which include CT internal and annulus pressures, and casing collar locator (CCL), for precise depth control and accurate correlation of well parameters.

In the south of Pakistan, the tubing-casing annulus pressure of a high-temperature gas well increased to near flowing wellhead pressure at the tubing, giving a clear indication that at least one of the completion components had failed, resulting in flow of hydrocarbons to the annulus. Yet, the high wellbore temperature limited conveyance of conventional logging tools to assess downhole completion integrity. A thorough analysis of well hydraulics was first conducted to gather the possible options to identify the leak using DTS. This enabled the determination of a workflow aiming to create enough differential pressure to generate particular temperature disturbance. CT equipped with fiber optics was run and stationed across the complete wellbore length, and DTS data were acquired for approximately twelve hours under changing well conditions, including shut-in and flowing periods. The acquired temperature information for each phase, along with pressure information, helped to narrow down the location of possible leak points.

This methodology enabled the identification of a single, major leak point located at an expansion joint in the completion. The operator was able to riglessly set an annular plug to restore integrity, thus saving significant workover cost and time.
The Corrosion-Metallurgical Aspects of Sucker Rods and Their Oil Well Service Performance
Authors: Radd F.J. , McGlasson R.L.
Published: February 2020

Published in Petroleum Transactions, AIME, Volume 201, 1954, pages 73–80.

The mechanisms of corrosion and corrosion fatigue damages to sucker rods are examined from a fundamental electrochemical viewpoint, and the relationships of sucker rod microstructures to these damaging effects are defined. The common corrosive agents in crude oil production and storage are discussed as to types of attacks that they cause. The variations of fatigue strength with alloy content, surface preparation, and stress ranges are analyzed. Finally, conclusions are drawn as to how microstructures largely influence and control sucker rod performance.

Introduction

Greater than 90 per cent of the crude oil produced by artificial lift methods is produced through sucker rod pumping systems. In the USA each year more than $14 million is spent for sucker rods in new and old pumping installations. It is important to make this investment a wise one.

Essentially, the sucker rod system is a long series of steel rods, operating under alternating stress loadings and under mechanical vibrations, which connect the surface power source with the subsurface pump. These rods often operate in a variety of corrosive media, including water, brines, carbon dioxide, hydrogen sulfide, and air.

Basically, this paper is concerned with the problem of the behavior of certain steels in various corrosive media under high and dynamic stress patterns. The main objective of this paper is to show how, once, the stress effects and the corrosive environments are defined, one can still realize structural control and beneficial influence upon corrosion and corrosion fatigue.
Clinical Features and Survival of Pregnancy-Associated Breast Cancer: A Retrospective Study of 203 Cases in China
Authors: Han Bo-yue , Li Xiao-guang , Zhao Hai-yun , Hu Xin , Ling Hong
Published: February 2020

Purpose: Pregnancy-associated breast cancer (PABC) is an aggressive disease, and sinceChinese authoritybegan to encourage childbearing in 2015, the incidence of PABC has increased. This study investigated the characteristics and survival of PABC patients. Methods: Patients with PABC who underwent surgery at Fudan University, Shanghai Cancer Center between 2005 and 2018 were enrolled.Data concerning the tumor characteristics, maternal state (whether first or non-first pregnancy ) and survival outcome were recorded. Pearson Chi-square tests were used to compare the characteristics of the tumors, and Kaplan-Meier methods were used to perform the survival analysis. Results: Overall, 203 PABC patients were recruited. Since 2015, 65.5% of non-first pregnant women were diagnosed with breast cancer, it’s 5.7 fold of the incidence of PABC in non-first pregnant women. No significant differences in tumor characteristics were observed between the patients who were in their first pregnancy and those in non-first pregnancy. Among the entire PABC population, luminal B breast cancer accounted for the largest proportion (38.4%), followed by triple-negative breast cancer (TNBC, 30.0%). The distribution of the molecular subtypes of PABC and non-PABC differed (P<0.001) as follows: in the PABC patients, Luminal B 38.4%, Triple negative breast cancer (TNBC) 30.1%, Human Epidermal Growth Factor Receptor 2 (HER-2) overexpression 15.8%, and Luminal A 10.8%; in the non-PABC patients, Luminal A 50.9%, Luminal B 20.1%, TNBC 17.4%, and HER-2 overexpression 8.0%. The 3-year disease free survival (DFS) of all PABC patients was 80.3%. The 3-year DFS of the patients in the first-pregnancy group was 78.4%, and that of the patients in the non-first-pregnancy group was 83.7% (P=0.325). Conclusions: Our study proved that the proportion of women who developed PABC during the second or third pregnancy was extremely high relative to the newborn populations. The patients in the PABC population tended to present more luminal B and TNBC breast cancer than the non-PABC patients.
Why institutional delivery is still the last option to rural women in North West Ethiopia: Qualitative study
Authors: Babbel Netsanet Fentahun , Wasihun Yosef , Mekonnen Wubegzier , Alemayehu Mulunesh Alemayehu Mulunesh
Published: February 2020

Background: Whatever the actions has been implemented, home delivery preference in Ethiopia is still over 72%. To date, no studies explored why institutional delivery is still the last option to rural women in Ethiopia. This study was conducted to explore the reason why institutional delivery is still the last option to rural women in Awi Zone Northwest Ethiopia.
Methods : An explanatory qualitative study was conducted from February to March 2014. Participants were selected purposively and written informed consent was sought. Twelve reproductive aged females, ten religious and twelve community leaders and sixteen key informants were participated. Data were collected by using semi-structured questionnaire using focused group discussion and in-depth interview guides. Thick description and peer debriefing were applied to assure data quality. Thematic analysis framework was used to analyse the data.
Results : The study revealed that institutional delivery is still the last option to the study area. Individual related factors like information gap, low risk Perception to pregnancy and delivery have been mentioned as drive factors for not using institutional delivery. Community related factors of women’s poor position to decision, beliefs and cultural practices for home delivery preference affects institutional delivery. In addition, health facility related barriers like inaccessibility of health facility, infrastructure, lack of privacy during delivery, misconducts of health care providers and high risk perception to health facility delivery were repeated raised as reasons of last option of institutional delivery.
Conclusion: This study elucidated that home delivery preference was existed, given high social and cultural price for home delivery and misconceptions towards institutional delivery. Thus, the Ethiopian government together with its partners should focus on accessing health facilities, infrastructure, equipping health facilities with essential materials and skilled health professionals and increasing knowledge of the community, avert communities’ misconceptions and deep-rooted socio-cultural beliefs towards institutional delivery.
EphB4/ TNFR2/ERK/MAPK signaling pathway comprises a signaling axis to mediate the positive effect of TNF-α on osteogenic differentiation
Authors: Zhang Yu , Yang Chengzhe , Ge Shaohua , Wang Limei , Zhang Jin , Yang Pishan
Published: February 2020

Background : Low concentrations of tumor necrosis factor-alpha (TNF-α) and its receptor TNFR2 are both reported to promote osteogenic differentiation of osteoblast precursor cells. Moreover, low concentrations of TNF-α up-regulate the expression of EphB4. However, the molecular mechanisms underlying TNF-α-induced osteogenic differentiation and the roles of TNFR2 and EphB4 have not been fully elucidated. Results : This study showed that with increase in ALP activity, mRNA and protein expression of RUNX2, BSP and EphB4, TNFR2 expression was significantly promoted under 0.5 ng/ml TNF-α stimulation in osteoblast precursor cells MC3T3-E1. After TNFR2 was inhibited by gene knockdown with lentivirus-mediated shRNA interference or by a neutralizing antibody against TNFR2, the pro-osteogenic effect of TNF-α was partly reversed, but up-regulation of EphB4 by TNF-α kept unchanged. With EphB4 forward signaling suppressed by a potent inhibitor of EphB4 auto-phosphorylation, NVP-BHG712, TNF-α-enhanced expressions of TNFR2, BSP and Runx2 were significantly decreased. Further investigation into the signaling pathways revealed that TNF-α significantly augmented expression of p -JNK, p -ERK and p -p38, however, only p -ERK expression was significantly inhibited in TNFR2-knockdown cells. In addition, the ERK pathway inhibitor, U0126 (10μM), significantly inhibited the protein levels of RUNX2 and BSP when compared with cells treated with TNF-α only. Conclusions : The EphB4, TNFR2 and ERK/MAPK signaling pathway comprise a signaling axis to mediate the positive effect of TNF-α on osteogenic differentiation.
Untreated dental caries prevalence and impact on the quality of life among 11 to14-year-old Egyptian schoolchildren: A cross-sectional study
Authors: Eid Samar , Khattab Nagwa , Elheeny Ahmad
Published: February 2020

Background
This study aimed to assess caries prevalence and experience among 11-14 years, school children, analyze demographic, socioeconomic, personal and professional dental care in relation to untreated carious lesions, and evaluates the effect of decayed teeth on early adolescents’ oral health-related quality of life (OHRQoL) .
Methods
A cross-sectional analytical investigation conducted on 1020 preparatory schoolchildren selected on the basis of a multistage sampling technique. Caries status of the participants detected via recording their caries experience and untreated cavities using DMFT and DT indices. OHRQoL was determined using a validated Arabic CPQ11-14 short-form questionnaire. Statistical methods for descriptive analysis, chi-square test, Independent-Samples T-Test and one-way analysis of variance (ANOVA) were used . Multi variate level Poisson regression analysis through a hierarchical approach was used to detect the influence of independent variables on DT scores. To declare the association between independent variables and QoL , a step-by-step, multivariate regression analysis was conducted .
Results
The average scores of DMFT and DT in this study were 2.97±1.29 and 1.66±1.24. Poisson regression analysis demonstrated that early adolescents whom their mothers with a lower level of education and of low socioeconomic status were 1.41 and 1.27 times respectively had higher DT scores when compared with their peers. Untreated cavities affected mainly by mother education, school type, family income, and regular dental appointments. Children with DMFT ≤ 3) or DT =0 recorded a statistically significant lower CPQ11-14 average score ( p ˂ 0.01) and ( p ˂ 0.0001) respectively.
Conclusions
Untreated carious cavities and caries experience were associated with lower socioeconomic, maternal education And less frequent tooth brushing. Untreated carious cavities have a significant negative impact on schoolchildren’s QoL .
Detection of Cercopithifilaria bainae infection in shelter dogs and ticks in Oklahoma, USA
Authors: Lineberry Megan W. , Sundstrom Kellee D. , Little Susan E. , Stayton Erin M. , Allen Kelly E.
Published: February 2020

Background

Cercopithifilaria bainae is a filarioid nematode of dogs. Infection with the parasite was not reported in the USA until 2017, when a dog with skin lesions in Florida was diagnosed. Brown dog ticks, Rhipicephalus sanguineus sensu lato, are the purported tick vectors, and are widespread in the USA. Therefore, C. bainae is likely present in additional states. Here, we tested dogs and ticks in Oklahoma for evidence of C. bainae infection.

Methods

Dermal punch biopsies were opportunistically collected from municipal shelter and client-owned dogs. Multiple skin samples collected from interscapular and head regions were tested by saline sedimentation to recover live microfilariae for morphometric identification and by PCR to amplify a 330 bp region of the filarioid 12S rRNA gene. Also, ticks observed on surveyed dogs were collected, identified to species level, and tested for filarioid DNA.

Results

A total of 496 saline sedimentations were performed on 230 shelter and 20 client-owned dogs. Cercopithifilaria bainae infections were identified in 2.6% (6/230) of shelter dogs by morphometry of microfilariae in sedimentations and/or amplification of DNA from skin. DNA sequences amplified from PCR positive skin samples were 99–100% identical to C. bainae reported in Italy. All skin samples from client-owned dogs were negative for filarioid infection by saline sedimentation and PCR. A total of 112 ticks, comprised of four species, were collected. Two of 72 R. sanguineus s.l., both engorged females found attached to a C. bainae infected dog, harbored C. bainae DNA (99–100% identity). One attached R. sanguineus s.l. male on the same dog harbored filarioid DNA sequence which was difficult to interpret at numerous base-pair locations, but was closest in identity (~80%) to C. bainae .

Conclusions

The distribution of C. bainae is more widespread than previously known. Here, we document C. bainae infections in dogs and DNA in brown dog ticks in Oklahoma for the first time. As brown dog ticks are commonly found throughout the USA, veterinarians in this region should consider C. bainae infection as a differential diagnosis in canine patients with dermatitis or polyarthritis.
Development of Leishmania (Mundinia) in guinea pigs
Authors: Bečvář Tomáš , Siriyasatien Padet , Bates Paul , Volf Petr , Sádlová Jovana
Published: February 2020

Background:

Leishmaniasis is a human and animal disease caused by parasites of the genus Leishmania , which is now divided into 4 subgenera – L. (Leishmania) , L. (Viannia) , L. (Sauroleishmania) and L. (Mundinia) . Subgenus Mundinia, established in 2016, is geographically widely dispersed, its distribution covers all continents, except Antarctica. It consists of 5 species - L. enriettii and L. macropodum are parasites of wild mammals while L. martiniquensis , L. orientalis and unnamed L . sp. from Ghana are infectious to humans. There is very little information on natural reservoir hosts and vectors for any Mundinia species.

Methods:

Experimental infections of guinea-pigs with all five Mundinia species were performed. Animals were injected intradermally with 10 7 culture-derived promastigotes into both ear pinnae. The courses of infections were monitored weekly; xenodiagnoses were performed at weeks 4 and 8 post infection using Lutzomyia migonei . The distribution of parasites in different tissues was determined post mortem by conventional PCR.

Results:

No significant differences in weight were observed between infected animals and the control group. Animals infected with L. enriettii developed temporary lesions at the site of inoculation and were infectious to Lu. migonei in xenodiagnoses. Animals infected with L. martiniquensis and L. orientalis developed temporary erythema and dry lesions at the site of inoculation, respectively, but were not infectious to sand flies. Guinea pigs infected by L. macropodum and L . sp . from Ghana showed no signs of infection during experiments, were not infectious to sand flies and leishmanial DNA was not detected in their tissue samples at the end of experiments at week 12 post-inoculation.

Conclusions:

According to our results, guinea pigs are not an appropriate model organism for studying Mundinia species other than L. enriettii. We suggest that for better understanding of L. (Mundinia) biology it is necessary to focus on other model organisms.

Key words:

Leishmania, Mundinia , guinea pig, Leishmania enriettii, Leishmania martiniquensis, Leishmania orientalis, Leishmania macropodum, animal model