bluuebunny/crossref_metadata_2025 huggingface dataset:
Mature Field Gas Lift Optimisation: Challenges & Strategies, Case Study of D-field, Malaysia
Authors: Ismail Wan Rokiah , Trjangganung Kukuh
Published: May 2016

As the world's population continues to grow, the energy demand is forecasted to increase directly proportional by 52% in between 2010 to 2035 (OPEC, 2013). With the oil prices predicted to be stable in the long run and expected to be as high as $165 per barrel by 2035, the search for more oil continues (OPEC, 2013). An estimation of 70% world's oil and gas production originates from mature fields with recovery at an average of 35% worldwide (Hull, 2012). This proves that there are still opportunities to recover more through enhanced primary, secondary or tertiary recovery in creating further hydrocarbon flow of a mature field.

Lower reserve with high operating and field redevelopment cost for a tertiary recovery program has deteriorated the economics for a mature field. Developing tertiary recovery for a mature field requires major modification at surface and sub-surfac, leaving the operators with the challenge to maximize recovery under current operating conditions and limited work scope of a primary recovery mainly through artificial lift method such as gas lift in oil wells.

Gas lift has been part of the primary oil recovery ever since the 1800s and the effectiveness has proven to aid the acceleration of oil recovery in a well for centuries (Gas Lift: Wikipedia, 2014). Deterioration in surface equipment and sub-surface well completion condition in a mature field, such as worsening well integrity with leaks and holes, inaccurate production metering, instability of gas compressor availability and efficiency, has resultant in the ineffective of gas lift distribution and injection downhole.

Despite the challenges faced, through prudent technical analysis and effective execution at site, the production of D-field in Malaysia has managed to increase up to 8,000 bbl/d (barrel of oil per day) instantaneously merely through production and gas lift optimization exercise.

This paper will run through the challenges faced and the technical analysis conducted in overcoming the handicap at site. This has led to the successful implementation/formulation of production philosophy and strategy to overcome challenges under different production scenarios, resulting an instantaneous production gain of some 30%. To some extent the production has been sustained and the decline arrested.
Chasing New Deep Play in South Malay Basin
Authors: Mohamad Firdaus , Abdullah Muhammad Shahril , Kahar Ruszaidi
Published: May 2016

Malay Basin is a relatively matured basin which has undergone exploration and production for more than three decades, mainly from stratigraphic units of Miocene to Late Oligocene. The matured nature of the basin has driven PETRONAS to evaluate the remaining deep play potentials.

DD is a deep prospect below D Field. Several pre-drill risks were identified during prospect maturation namely, high temperature (450F), high pressure (11000 psi) and poor reservoir quality with low porosity (6% to 12%) and low permeability of <1 mD. PCSB however decided to drill DD-1 due to its large four way dip closure (approximately 250 km2), volume in-place and potential to open up other deep plays.

DD-1 is PETRONAS' first Ultra High Pressure High Temperature (HPHT) well, located in southern Malay Basin to evaluate gas in Group M (Early Oligocene age). It penetrated Group M in D Field and reached its final TD at 4350 m TVDSS. It recorded temperature and pressure of 488oF and 13900 psi respectively. DD-1 proved that the petroleum system is working for the deep play by intersecting several gas bearing sandstone units namely M20, M30, M60 and M70 (C1-nC5, total gas 5% to 13%). Reservoir effectiveness is the major issue - low porosities (3% to 8%) and extremely low permeability (0.0025mD). Well testing over M20 flowed gas to surface and was flared, however the testing was deemed inconclusive. The HPHT nature of the well also presented operational challenges such as drilling within narrow mud weight and fracture gradient margin and the availability of suitable HPHT logging tools.

Well results indicated that Group M was gas bearing; however at this stage is not commercially recoverable. The deep play potential remains to be commercially exploited but better understanding of natural fracture networks and the utilising of advanced technology will be required.

1.0 Introduction

DD-1 well is located approximately 236 kilometers northeast of Kemaman Supply Base (KSB), in water depth of 75 meters offshore Peninsular Malaysia (Figure 1). The prospect basically lies below the existing D Field which is currently being produced from the shallower Group I, J, K and L reservoirs.

The primary objective of the proposed DD-1 is to evaluate the hydrocarbon potential of the Group M sandstones which are within a structural four-way dip closure, the first ever well to test Group M in D Field. DD-1 is PETRONAS' first Ultra High Pressure High Temperature (HPHT) well; it was spudded on 01 March 2013 and after five months of drilling campaign, it successfully reached final TD at 4388 m MDDF on 18 July 2013. It experienced high temperature and high pressure of 488oF and 13900 psi at final TD.
Successful Application of Customized Fluid Using Specialized Synthetic Polymer in High Pressured Wells to Mitigate Differential Stikcing Problems by Minimizing Pore Pressure Transmission
Authors: Al-Muhailan Mohannad Sulaiman , Rajagopalan Arun , Al-Shayji Al Aziz Khalid , Jadhav Prakash Balkrishna , Khatib Faiz Ismail
Published: May 2016

Drilling deep wells in Kuwait has become a challenge due to excessive overbalance pressures up to 3,500 psi applied across a highly permeable sandstone/shale formation. High differential pressures leading to tight hole, string stalling, differentially stuck pipe and induced losses contribute to considerable non-productive time. The existence of a high pressure salt zone below this interval and a seven casing string design removed the further option of zonal isolation by casing. Traditionally, oil based mud with Calcium Carbonate of different sizes was used to reduce fluid invasion, but with limited success.

A customized fluid system was designed to overcome the issue of high overbalance pressure targeting improved bridging, minimized pore pressure transmission and wellbore strengthening with increased hoop stress. Software modelling and permeability plugging tests were performed to evaluate the fluid behavior under downhole conditions and to predict the characteristics of induced micro fractures based on rock mechanics. Porosity, permeability and induced micro fractures were considered to optimize the bridging mechanism. These results identified a synthetic deformable sealing polymer combined with sized graphite and ground marble showed considerable improvement in minimizing filtrate spurt loss without altering the rheological parameters and stability of the OBM.

A inclined well in sandstone/shale formation was selected for the application after suffering multiple wellbore instability and differential sticking incidents, resulting in more than 800 hours of non-productive time and a sidetrack. The new inclined section was successfully drilled with a stable wellbore, smooth trips, and no tight hole or sticking incidents. The borehole remained completely stable, even after 16 hours of 13 5/8" casing string suspended in 16" open hole without circulation.

This paper analyzes the historical problems encountered in this sandstone/shale formation, and presents the solutions developed based on these problems and case histories of the successful field application of this customized fluid.
Offshore Sub-Basalt Exploration Using CSEM and MT
Authors: Panzner Martin , Kumar Krishna , Mrope Frida
Published: May 2016

Seismic sub-basalt imaging is challenging and often leaves remaining uncertainties about the sub-basalt structures. This paper considers how the marine controlled source electromagnetic (CSEM) and the magnetotelluric (MT) method can reduce the interpretation uncertainty by providing structural and quantitative resistivity information about the thickness and extent of the basalt sequence and the sediments below. In order to demonstrate the capability of these technologies, we will present two recent studies: (1) a synthetic inversion test from a realistic model based on well-log and seismic data and (2) inversion of field data acquired over the Faroe-Shetland Escarpment. We will show that this information can also be used to improve the velocity models for seismic depth imaging.

Introduction

Basalts are extrusive igneous rocks that can be found worldwide. Often the compact basalts are interlaid with volcanoclastics and sediments. Such sequences are formed by a series of eruptive events. Sub- and intra-basalt sediments can be hydrocarbon bearing, which makes sub-basalt exploration very interesting to the oil and gas industry.

Using seismic, one can usually establish the top of the basalt accurately. But due to the heterogeneities in the basalt layer in combination with high seismic impedance contrasts it can be challenging to accurately image the base of the basalt and underlying sediments (Fliedner and White, 2001; Fruehn et al., 2001). Conversely, several modelling and inversion studies have shown that EM methods can play a significant role in mapping both the thickness of the basalt layer and the sediments below (Jegen et al, 2002; MacGregor, 2003; Hoversten et al.,2013; Heincke et al., 2014).

The CSEM and MT methods utilize electromagnetic (EM) fields to measure resistivity variations in the sub-surface. Compact crystalline rocks such as basalt have virtually no porosity and are very resistive in contrast to sediments with comparably large pore spaces filled with more conductive pore fluids. That makes EM methods well suited for imaging of the thickness of the basalt layer and the structures underneath. In this paper, we discuss two studies, (1) a synthetic data study based on a realistic model (Herredsvela et al., 2012) and (2) a field data example from the Faroe-Shetland Basin.

Synthetic Basalt Model

Figure 1 shows the model which was used for the synthetic modelling and inversion study. The water depth in the model varies from 300 to 350 m. The model consists of a fine layered basalt sequence with a varying thickness from 200 meters to almost 2 kilometers and a detailed sediment structure underneath the basalt. The internal structure of the basalt sequence is based on the observations from well logs and seismic. It consists of many thin layers with varying resistivities which are sensed as one thick anisotropic layer due to low resolution of the EM methods. The information used to construct this model makes it analogue to a realistic scenario.
Early Meteoric Diagenesis and Porosity Preservation: Stratigraphic Traps in Carbonate Grainstones
Authors: Major R P
Published: May 2016

It is well established that aragonite sediment can be rapidly cemented in near-surface diagenetic environments when exposed to meteoric (fresh) water. Indeed, there are published examples of calcite cementation of aragonite sediments that resulted in rocks hard enough to require a hammer for sampling, and some of these examples formed in time periods shorter than a human lifetime. Complete mineralogic stabilization requires longer time periods, although within meteoric phreatic lenses in humid environments alteration to 100 percent low-magnesium calcite can occur as quickly as 5,000 years.

Early lithification, especially lithification and complete mineralogic stabilization in paleophreatic lenses, has been demonstrated to produce zones within carbonate rocks that are more resistant to compaction and porosity destruction during burial than superjacent and subjacent rocks. Thus, early exposure to meteoric phreatic diagenesis is one mechanism for producing stratigraphic traps; that is, hydrocarbon reservoirs in which the trapping mechanism is not controlled by structural deformation.

Introduction

Ehrenberg et al. (2012) reviewed numerous published examples of porosity in carbonate rocks interpreted to have formed by late-stage burial dissolution and concluded that most of these interpretations were based on equivocal data. Although Ehrenberg et al. are perhaps too quick to dismiss some very well documented examples of this phenomenon, their principal conclusion seems at least consistent with what is known about the burial diagenetic environment. That is, in contrast with near-surface diagenetic environments in which several mechanisms can move a great many fluid pore volumes through a sediment in geologically short periods of time, fluids in burial diagenetic environments move sluggishly and generally do not have an obvious exit pathway. Thus leaching in burial diagenetic environments, although clearly important in some hydrocarbon reservoirs, is probably neither common nor volumetrically significant in the stratigraphic record.

It has been well documented that the general fate of porosity in carbonate sediments and rocks is progressive destruction during burial (for example, Schmoker and Halley, 1982). Thus, porous and permeable rocks at depth, i.e. reservoirs, are the anomalies rather than the generalization.

If one accepts these two generalities: late-stage leaching is rare and porosity is normally destroyed during burial, then it follows that porosity preservation during burial is at least one important factor in the formation of hydrocarbon reservoirs. This paper reviews one mechanism for preserving porosity during burial that may be quite common.
Foams Prove Effectiveness for Gas Injection Conformance and Sweep Efficiency Improvement in a Low porosity Fractured Reservoir – Field Pilots
Authors: Ocampo-Florez Alonso , Restrepo Alejandro , Rendon Natalia , Coronado Jorge , Correa Juan Alejandro , Ramirez Diego Alejandro , Torres Monica , Sanabria Rosa , Lopera Sergio Hernando
Published: May 2016

Foams have proved to be efficient to block temporarily high conductivity layers, and improving gas injection conformance and sweep efficiency in predominantly matrix reservoir systems, at least at lab and field pilot tests; nevertheless, its successful use in naturally fractured reservoirs has not been fully demonstrated as of today. This paper presents the evaluation process and the successful results for two (2) foam EOR field pilots performed in the Cupiagua in Recetor field; a gas condensate system whose main reservoir is a low porosity (<6%) quartzarenite with matrix permeabilities in the range of 0.01 to 10 mD, and where the fracture corridors are confirmed to play an important role both in well productivity/injectivity, and in the inter-well connectivity and gas channelling between gas injectors and oil producers.

The reservoir has been developed under massive hydrocarbon gas re-injection, and the current recovery factors of condensate are between 35–40%. The foam treatments were deployed in two gas injectors located in different areas of the field, each one impacting two oil producers, and exhibiting different levels of gas recycling, with GOR ranging between 40,000 and 100,000 scf/STB.

Both operations were performed via bull-heading using the SAG method. The results for both jobs showed a temporary reduction in gas injectivity, with slow recovery to its base line within the next 3 months. Despite showing little changes in the injection profile at the gas injectors, the two producers affected by the first job showed a clear change in GOR trends, and a consistent ramp-up in oil production rates during a period of at least 7 months, reaching a maximum increase between 15 and 30 % over their base line productions. The second job was performed to confirm consistency and repeatability of technology, and evaluate duration cycle of blocking and benefit effects. Early surveillance indicates positive response both at the gas injector, and the oil producers. Results herein presented, confirm the viability for foams as an EOR method for this naturally fractured field, and open EOR opportunities for other fractured reservoirs located in the same basin and exploited under gas injection schemes.
THE INTEGRATION OF PETROLEUM SYSTEMS ELEMENTS FOR HYDROCARBON PROSPECTING IN PRE-MESSINIAN STRATIGRAPHIC SECTION OF THE OFFSHORE WEST NILE DELTA, EGYPT
Authors: Keong Ong Swee , Bt. Abdullah Azirul Liana , Bin Ahmad Fuad Ahmad Syahir , Bt Hamdan Norazean , Bt Anuar Azlina , Basu Debnath , Ysaccis Raul , Murthy K S , Kim Taesoo
Published: May 2016

The study area is situated in the offshore West Nile Delta basin towards the northeast of Alexandria, Egypt. This is a major petroleum habitat hosting many gas and condensate fields. The present paper summarizes the petroleum system elements for hydrocarbon prospecting in the Messinian and deeper stratigraphic section based on an integrated study of seismic and well data.

Mixed well results have been observed in the area with proven gas fields found in stratigraphic fluvial channels in the Messinian. Rotated fault blocks and fault dependent traps were tested but no discoveries were proven. Failure could be due to trap integrity issues and inadequate migration pathways. Potential remaining stratigraphic plays identified are deepwater slope channels in the pre-Messinian to Oligocene section similar to overlying Pliocene gas fields.

Depositional models based on seismic attribute mapping and a few wells generally depicts a NW-SE facies belt trend dominated by deepwater slope channel complexes flanked by slope shales ranging in age from Upper Oligocene to Miocene (Pre-Messinian). In the Messinian, the depositional environment is associated with a major sea-level drop with consequent exposure of the shelf/slope. It contains predominantly incised valleys and fluvial-fills flanked by interfluves.

The hydrocarbon charge is expected from Cretaceous-Jurassic and Early Tertiary pro-delta shale source rocks (Marten et al., 2004). Evidence of highly mature thermogenic gases (2.0 % - 2.5% VRo) advocates the assumption of the presence of a deeper source rock contribution from limited well calibration. Basin modeling results shows that the modelled source rocks are presently in the hydrocarbon generation window. Source rock generation has occurred very late from 9.0Ma to 1.0Ma and migration timing post-dates trap formation. Traps are expected to be charged vertically and through fault conduits as observed in well results.

This study paved the way for a better understanding of the petroleum system elements which consequently forms the basis in risking the Messinian and deeper exploration plays and shows that the Messinian stratigraphic channel plays are most prospective.
Automated Racking-Board Pipe-Handling System Eliminates Hazards of Tripping Operations, Reduces Rig Personnel, and Creates Consistent Tripping Speeds in Line with Best Rig Crew Performance
Authors: Jaber Adham Sultan
Published: May 2016

Tripping of drill pipe is known to be one of the most dangerous and physically demanding jobs on the rig and involves a derrickman and rig floor hands that are often subject to various injuries. Now this hazardous operation can be automated, which moves personnel out of harm's way and simultaneously creates attractive and very consistent tripping results.

In this paper we will discuss field experiences while introducing such a system into an active onshore drilling operation in Canada. The unit is lightweight and fit for first installations, or it can serve as a retrofit-capable package. The Iron Derrickman S3 comes with a custom racking board that pins directly in the place of a conventional racking board. Complete with a standalone control system and power unit, it makes for a quick and easy addition to any rig. It immediately increases safety by actually removing the Derrickman from his exposed position and simultaneously making a floor hand redundant. The reduced incident exposure realized from removing the need for a Derrickman to climb up the mast and manhandle a nearly 9000lb stand of pipe with the supporting floor hands on the rig floor that control the bottom of the stand (in the red zone) and drive it around the floor each time a stand of pipe is needed, is tremendous. As you can see in the IADC Industry LTI's numbers from 2013, the incidents on the floor, in the racking board and involving Derrickman make up the lion's share of all LTI's on the rig annually. The Iron Derrickman S3 is an engineered solution that will help eliminate these hazards.
Tight Fractured Reservoirs: a Challenging Environment For LWD Operations Optimization & Fluid Path Detection
Authors: Pampuri Ferdinanda , Berto Roberto , Borghi Massimiliano , Casero Arabella , Firinu Mauro
Published: May 2016

The huge number of horizontal wells drilled in complex reservoirs and the development of more accurate logging while drilling (LWD) technologies offer to the oil&gas companies the opportunity to reduce operational risks and save time and costs, by replacing wireline acquisition with LWD tools.

This paper describe a new acquisition strategy based on advanced LWD tools recently made available also in 6" hole size. Thanks to this technology it was possible to provide a reliable reservoir characterization and to identify the best fluid path in horizontal infilling wells drilled into tight and fractured carbonatic reservoir.

Economic and HSE aspects have been strongly considered in the illustrated strategy.

The integrated analysis of advanced sonic and resistive image while drilling logs provided the essential information to quantify the matrix and the secondary fractured porosity as well as the "mixed" porosity, and, in addition, fundamental data to clarify the reservoir quality where Tough Logging Conditions (TLC) cannot be through.

The acoustic compressional arrivals contribute to porosity evaluation while the Stoneley waves interpretation allowed the detection of "open" natural fractures.

In addition, recognized "open" fractures have been matched with mud losses events, Gas While Drilling and temperature profile. The producible intervals identified by the illustrated methodology agree with the response of the main production results.

The approach has been validated by means of an accurate comparison between wireline and while drilling logs response, both available along an interval of a reference well section. The LWD technology has shown its capability to capture the different scale of phenomena occurring into fractured reservoirs.

Thanks to the combination of technology, knowledge and people, well data acquisition can be conducted safely and with significant saving in term of operating time reduction. The additional information about fluid path detection can improve the efficiency of the well completion.

INTRODUCTION AND SCOPE OF WORK

The strong and continuous need to drill and produce high deviated or horizontal wells in the oil business was a heavy impulse to change vision on tool conveyance method moving from Wire Line (WL) to Logging While Drilling (LWD) acquisitions.

The service companies in the last years spent a lot of effort in the LWD tool development and now days the quality and the completeness of the last generation LWD is comparable with the wire line technology in most case, and more useful in others. The operators choose the logging data acquisition strategy, while drilling or after drilling, based on project requirements.

The LWD tool application not only can provide good performance but can also be an important opportunity to increase efficiency and safety.

Few technologies have had a larger impact on these results than Logging While Drilling (LWD).
The impact of rock pore structure on Co2 relative permeability
Authors: Traki Adel Ragib , Sohrabi Mehran
Published: May 2016

Co2 relative permeability is a critical parameter affecting many aspects of Co2 injection for Enhanced Oil recovery and Co2 storage including; injectivity and trapped phase saturation.

In this study, we use measured Co2 - brine relative permeability data available in the literature to study the behaviour of the data obtained for various rocks. These measured Co2 relative permeabilities show large variations in the values of relative permeability and also in the trend of the relative permeability curves.

We identify the rock internal structure or quality as a controlling factor with considerable impact on Co2 relative permeability and we offer an explanation for the observed variation in Co2 relative permeability behaviour. We use a pore network model with different pore and throat distributions to verify the effect of rock pore and throat distributions on Co2 relative permeability. Based on our definition, a normal pore-throat distributions with similar connection produces a regular Co2 relative permeability curve shape which gives a high Co2 injection rate whereas in an abnormal pore-throat distribution with dissimilar connection, it is observed that the Co2 relative permeability curve shape is almost vertical.

We extended the work to the investigation of the impact of the rock internal structure on the Co2 injection characteristics particularly on Co2 injection rate. We found that normal pore-throat distributions with similar connection result in much higher Co2 injection rate than do the abnormal pore-throat distributions with dissimilar connection.

The results of this study will allow us to identify rocks that would be more suitable for Co2 injection (e.g., higher injectivity requiring lower number of injection wells) on the basis of the structure and distribution of the pores inside the rock.

Introduction and Objective.

In most petroleum engineering literatures, the relative permeability of Co2 has been studied for each formation separately and the main factors considered to affect the Co2 relative permeability are; fluid saturation, hysteresis and interfacial tension. As for a group of formations with different rock types, the difference in Co2 relative permeability curves is mainly attributed to rock type parameters. However, it has been found that even in a set of samples extracted from different formations in the same rock type or from a single formation, there is diversity in Co2 relative permeability curves. Rock pore structure or quality has been assumed to be responsible of the observed disparity, but no detailed explanation has been offered as to how it could results in different Co2 relative permeability curves for a set of formations in the same rock type. In this work, we are introducing an improved concept of pore and throat distribution, which will be used to interpret the observed differences in Co2 relative permeabilities.
Maintaining Reliable Operation of Aging Gas Compressors Using Novel Repair Techniques
Authors: Edward Karl , Chin T H , Uptigrove Stan
Published: May 2016

As upstream oil and gas facilities age, it is a constant challenge to maintain equipment reliability and uptime while managing cost pressures and changing production rates that are significantly different from design. This challenge can be effectively met by properly managing repairs rather than replacing failed equipment with new units. In fact, with the right engineering, the repair can improve equipment availability over a straight replacement. This paper provides two case studies where non-standard equipment repairs were executed to improve reliability while reducing repair costs and downtime.

Case Study 1: Eroded Compressor Diaphragm

As reservoirs deplete and enhanced recovery methods are employed, it is possible to experience increased levels of solids, sand and water. Over time, this leads to erosion in process machinery such as compressors and pumps. The paper describes how a badly eroded compressor diaphragm was repaired via a brush plating repair methodology. Although this technique had not been used before by the operator or the Original Equipment Manufacturer (OEM), a collaborative effort was successful in evaluating and implementing the repair.

Case Study 2: Combining Two Failed Gearboxes into One Functional Unit

An oil production facility experienced coupling failures on two neighboring machines a few weeks apart that resulted in collateral damage to the gearboxes. Initial investigation found that the gearbox output rotors had suffered yielding at the tapered area of the coupling hub. Run-out and concentricity measurements indicated that the gear rotors were not fit for service and needed to be replaced. However, the gas turbine driven compression train was scheduled for final decommissioning a year after the time of the failure following over 30 years of reliable operation. A spare set of gear rotors was not available as they had never required replacement before. The subsequent procedures and execution of repairs utilizing parts from the two gear boxes to produce one functional gear box are described.
Wellbore Instability Analysis for Highly Fractured Carbonate Gas Reservoir from Geomechanics Prospective, Saudi Arabia Case Study
Authors: Al-Nutaifi Abdulrahman Muhammed , Abdulraheem Abdulazeez , Khan Khaqan
Published: May 2016

A major challenge facing the oil and gas drilling operations is mitigating the encountered wellbore instability issues. Those can vary from loss circulations up to having stuck pipes or tools that may jeopardize well integrity and potentially lead to total loss of wells and assets. These problematic situations are even much more complicated in fractured reservoir environments where predicting the fracture density is important. Analyzing such problems is critical for companies especially in developing offshore fields where one day lost time is in hundreds of thousands of dollars. The field of rock mechanics emerged to connect those phenomena to reservoir rock properties and stress profiles. Coupling this with an intensive analysis of drilling parameters, logging, core testing and other existing wells data builds a work frame that helps in understanding the reasons behind wellbore failures and providing solutions to them. The field under investigation is a highly geo-pressured offshore gas field. The field development called for drilling vertical and deviated wells. During the field increment sever loss circulation were encountered that resulted in lost drilling times estimated in millions of US dollars with rig cost up $ 200,000/Day. Other drilling failures includes, stuck drill pipe and difficulties with logging response and log interpretation. The objective of this study is to investigate the wellbore instability during drilling operations as function of rock properties, in-situ earth stress and drilling parameters. Emphasis on the role of natural fractures density will be highlighted and included in modeling inputs as well as characterizing its density across the field. During the course of the study, existing field's and drilled wells available data will be analyzed and a simulation models will be utilized to simulate the stress profiles in the field. Based on the results, the factors behind the instability issues in the field will be identified and recommendations will be made for future wells drilling programs.
Geopressure Centroid as Pore Pressure Prediction Challenge in Deepwater South East Asia
Authors: Kaeng Geovani Christopher , Sausan Sarah , Satria Andrean
Published: May 2016

Rapid sedimentation in the deep water of the young Tertiary basin in southeast (SE) Asia is one of the primary causes for the development of overpressured systems. In this setting, pore water is unable to escape naturally during deposition. This causes increased pore pressure above hydrostatic pressure. Shale porosity has often been used to estimate in situ fluid pressure. A typical approach is to examine the porosity profile in a zone of known fluid pressure (i.e., the hydrostatic zone) and then use this empirical relationship to predict pressure where it is unknown (i.e., the overpressured zone). The resulting shale based predictions are then compared to in situ fluid pressure measured in reservoir rock (e.g., sand). A difference between predicted and measured pressure is then interpreted simply as a deficiency of the model. However, a more recent belief is that, in overpressure zones, a pressure difference in sand and shale is not uncommon in the presence of structural inclination.

This study continues to explore differences between shale predicted pore pressure and in situ pressure in sand and how it affects well design. The authors interpret observed deviations between measurements and predictions as actual differences between sand and shale pressure attributed to lateral transfer of fluids along inclined reservoirs. The elevation where shale and sand pressure are in equilibrium is called a centroid effect.

Three offset wells are used to build a centroid model in Field DW for the purpose of predicting pore pressure in the proposed well located at the crest of the structure. Industry standard practice is followed to build the centroid model to help prevent pitfalls.

INTRODUCTION

Geopressure is the fluid pressure within earth formations, also referred to simply as formation pore pressure. High formation pressure exceeding normal hydrostatic pressure is termed overpressure (Dutta 1987). High formation pressure is typically found in young, rapidly deposited clastic rocks (primarily sandstone, shale, and siltstone) because of incomplete dewatering of fine-grained rock, such as shale, which is known as compaction disequilibrium (Osborne and Swarbrick 1997; Chapman 1994; Mouchet and Mitchell 1989). This process indicates that the more shale existing in the sedimentary succession, the greater the likelihood of high pressure. The amount of overpressure is a function of the permeability of the rock (how fast the water can escape when buried) and the rate of burial. However, there are other reasons for high pressure primarily related to deeper processes occurring in the rock column at elevated temperatures. It follows from the previous description of the mechanisms that three primary components control where overpressure occurs—rate of sediment burial, temperature, and sediment permeability.
Response of N, P and K on the growth and flowering of hippeastrum (Hippeastrum hybridum Hort.)
Authors: Jamil MK , Rahman M Mizanur , Hossain M Mofazzal , Hossain M Tofazzal , Karim AJM Sirajul
Published: May 2016

An experiment was conducted at the Horticultural Research Field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur during September 2008 to May 2009 to determine the response of hippeastrum (cu. Apple Blassom) to different combinations of nitrogen, phosphorus and potassium levels. There were 14 treatment combinations comprising four levels of nitrogen viz. 0, 100, 200, and 300 kgha-1; five levels of phosphorus viz. 0, 200,300, 400 and 500 kgha-1 and five levels of potassium viz. 0, 100, 200, 300 and 400 kgha-1 with an exclusively Cowdung treatment at the rate of 10 tha-1 . The experiment was laid out in a Randomized Complete Block Design with three replications. The growth and flowering parameter of hippeastrum were significantly influenced by combined application of N, P & K.The highest values in respect of leaves per plant (8.6), leaf breadth (5.4 cm), number of plants per bulb (3.07), flower scape per plant (2.07), flowers per scape (4.2), length and diameter of flower (14 cm x 13.83 cm), flower scape (43.33 cm x 29.37 cm) and flowering duration (10.7 days) were observed with N200P400K300. The same treatment showed earliness in days to flower scape emergence (172.3 days), days to flower bud appearance (185.3 days) and days to first flower open (189.3 days). The biggest flower (14.00 cm x 13.83 cm), longest flower scape (43.33 cm), maximum number of flowers per scape (4.20), and maximum flowering duration (11.5 days) were also exhibited by the treatment N200P400K300 .The control treatment (N0P0K0) recorded the lowest values except days to first leaf emergence, days to flower scape emergence, days to flower bud appearance and days to first flower open.Bangladesh J. Agril. Res. 41(1): 91-101, March 2016
The epidemiology of bacterial pneumonia in Black Bengal goats in Bangladesh
Authors: Momin MA , Islam MA , Khatun MM , Rahman MM , Islam MA
Published: May 2016

Goat pneumonia is commonly caused by infectious agents. The present study was conducted at Mymensingh Sadar (District headquarters) and Ullahpara Upazillas (Subdistrict). In each area goats with a history of pneumonia were identified. Age, sex, season, health status and hygienic practices of the affected flocks were recorded. Lungs and nasal swabs were collected from 250 Black Bengal goats for bacteriological examination. The prevalence of pneumonia was higher in young goats (1-12 months old) than in adults (>12 to 36 months old) (33% and 11.3%, respectively) (P<0.05). The prevalence in female goats was higher than in male goats (23.0% and 12.0%, respectively). In winter prevalence was higher (27.1%) than in summer (11.0%) (P<0.05).Bangl. vet. 2014. Vol. 31, No. 2, 70-73
From the Editors (German)
Authors: Namli Elena
Published: May 2016

No abstract available.
Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China
Authors: Li Minghui , Cao Jie , Li Wenpu
Published: May 2016

The permeability of coal is a critical parameter in estimating the performance of coal reservoirs. Darcy’s law describes the flow pattern that the permeability has a linear relationship with the flow velocity. However, the stress induced deformation and damage can significantly influence the gas flow pattern and permeability of coal. Coals from Songzao coalfield in Chongqing, southwest China were collected for the study. The gas flow velocities under different injection gas pressures and effective stresses in the intact coal and damaged coal were tested using helium, incorporating the role of gas flow pattern on the permeability of coal. The relationships between the flow velocity and square of gas pressure gradient were discussed, which can help us to investigate the transformation conditions of gas linear flow and gas nonlinear flow in the coal. The results showed that the gas flow in the intact coal existed pseudo-initial flow rate under low effective stress. The low-velocity non-Darcy gas flow gradually occurred and the start-up pressure gradient increased in the coal as the effective stress increased. The gas flow rate in the damaged coal increased nonlinearly as the square of pressure gradient increased under low effective stress. The instability of gas flow caused by high ratio of injection gas pressure over effective stress in the damaged coal contributed to the increase of the gas flow rate. As the effective stress increased, the increase of gas flow rate in coal turned to be linear. The mechanisms of the phenomena were explored according to the experimental results. The permeability of coal was corrected based on the relationships between the flow velocity and square of gas pressure gradient, which showed advantages in accurately estimating the performance of coal reservoirs.
Anticancer Activity of γ-Bisabolene in Human Neuroblastoma Cells via Induction of p53-Mediated Mitochondrial Apoptosis
Authors: Jou Yu-Jen , Hua Chun-Hung , Lin Chen-Sheng , Wang Ching-Ying , Wan Lei , Lin Ying-Ju , Huang Su-Hua , Lin Cheng-Wen
Published: May 2016

γ-Bisabolene has demonstrated antiproliferative activities against several human cancer cell lines. This study first discloses the antiproliferative and apoptosis induction activities of γ-bisabolene to human neuroblastoma TE671 cells. A CC50 value of γ-bisabolene was 8.2 μM to TE671 cells. Cell cycle analysis with PI staining showed γ-bisabolene elevating the sub-G1 fractions in a time-dependent manner. In addition, annexin V-FITC/PI staining showed γ-bisabolene significantly triggering early (annexin-V positive/PI negative) and late (annexin-V positive/PI positive) apoptosis in dose-dependent manners. γ-Bisabolene induced caspase 3/8/9 activation, intracellular ROS increase, and mitochondrial membrane potential decrease in apoptosis of human neuro-blastoma cells. Moreover, γ-bisabolene increased p53 phosphorylation and up-regulated p53-mediated apoptotic genes Bim and PUMA, as well as decreased the mRNA and protein levels of CK2α. Notably, the results indicated the involvement of CK2α-p53 pathways in mitochondria-mediated apoptosis of human neuroblastoma cells treated with γ-bisabolene. This study elucidated the apoptosis induction pathways of γ-bisabolene-treated neuroblastoma cells, in which could be useful for developing anti-neuroblastoma drugs.
Feedback Robust Cubature Kalman Filter for Target Tracking Using an Angle Sensor
Authors: Wu Hao , Chen Shuxin , Yang Binfeng , Chen Kun
Published: May 2016

The direction of arrival (DOA) tracking problem based on an angle sensor is an important topic in many fields. In this paper, a nonlinear filter named the feedback M-estimation based robust cubature Kalman filter (FMR-CKF) is proposed to deal with measurement outliers from the angle sensor. The filter designs a new equivalent weight function with the Mahalanobis distance to combine the cubature Kalman filter (CKF) with the M-estimation method. Moreover, by embedding a feedback strategy which consists of a splitting and merging procedure, the proper sub-filter (the standard CKF or the robust CKF) can be chosen in each time index. Hence, the probability of the outliers’ misjudgment can be reduced. Numerical experiments show that the FMR-CKF performs better than the CKF and conventional robust filters in terms of accuracy and robustness with good computational efficiency. Additionally, the filter can be extended to the nonlinear applications using other types of sensors.
Fuzzy-Based Hybrid Control Algorithm for the Stabilization of a Tri-Rotor UAV
Authors: Ali Zain , Wang Daobo , Aamir Muhammad
Published: May 2016

In this paper, a new and novel mathematical fuzzy hybrid scheme is proposed for the stabilization of a tri-rotor unmanned aerial vehicle (UAV). The fuzzy hybrid scheme consists of a fuzzy logic controller, regulation pole-placement tracking (RST) controller with model reference adaptive control (MRAC), in which adaptive gains of the RST controller are being fine-tuned by a fuzzy logic controller. Brushless direct current (BLDC) motors are installed in the triangular frame of the tri-rotor UAV, which helps maintain control on its motion and different altitude and attitude changes, similar to rotorcrafts. MRAC-based MIT rule is proposed for system stability. Moreover, the proposed hybrid controller with nonlinear flight dynamics is shown in the presence of translational and rotational velocity components. The performance of the proposed algorithm is demonstrated via MATLAB simulations, in which the proposed fuzzy hybrid controller is compared with the existing adaptive RST controller. It shows that our proposed algorithm has better transient performance with zero steady-state error, and fast convergence towards stability.
Cubature Information SMC-PHD for Multi-Target Tracking
Authors: Liu Zhe , Wang Zulin , Xu Mai
Published: May 2016

In multi-target tracking, the key problem lies in estimating the number and states of individual targets, in which the challenge is the time-varying multi-target numbers and states. Recently, several multi-target tracking approaches, based on the sequential Monte Carlo probability hypothesis density (SMC-PHD) filter, have been presented to solve such a problem. However, most of these approaches select the transition density as the importance sampling (IS) function, which is inefficient in a nonlinear scenario. To enhance the performance of the conventional SMC-PHD filter, we propose in this paper two approaches using the cubature information filter (CIF) for multi-target tracking. More specifically, we first apply the posterior intensity as the IS function. Then, we propose to utilize the CIF algorithm with a gating method to calculate the IS function, namely CISMC-PHD approach. Meanwhile, a fast implementation of the CISMC-PHD approach is proposed, which clusters the particles into several groups according to the Gaussian mixture components. With the constructed components, the IS function is approximated instead of particles. As a result, the computational complexity of the CISMC-PHD approach can be significantly reduced. The simulation results demonstrate the effectiveness of our approaches.
CoR-MAC: Contention over Reservation MAC Protocol for Time-Critical Services in Wireless Body Area Sensor Networks
Authors: Yu Jeongseok , Park Laihyuk , Park Junho , Cho Sungrae , Keum Changsup
Published: May 2016

Reserving time slots for urgent data, such as life-critical information, seems to be very attractive to guarantee their deadline requirements in wireless body area sensor networks (WBASNs). On the other hand, this reservation imposes a negative impact on performance for the utilization of a channel. This paper proposes a new channel access scheme referred to as the contention over reservation MAC (CoR-MAC) protocol for time-critical services in wireless body area sensor networks. CoR-MAC uses the dual reservation; if the reserved time slots are known to be vacant, other nodes can access the time slots by contention-based reservation to maximize the utilization of a channel and decrease the delay of the data. To measure the effectiveness of the proposed scheme against IEEE 802.15.4 and IEEE 802.15.6, we evaluated their performances with various performance indexes. The CoR-MAC showed 50% to 850% performance improvement in terms of the delay of urgent and time-critical data according to the number of nodes.
Fluoride Anion Recognition by a Multifunctional Urea Derivative: An Experimental and Theoretical Study
Authors: Schiller Jana , Pérez-Ruiz Raúl , Sampedro Diego , Marqués-López Eugenia , Herrera Raquel , Díaz Díaz David
Published: May 2016

In this work we demonstrate the ability of a multifaceted N,N′-disubstituted urea to selectively recognize fluoride anion (F−) among other halides. This additional function is now added to its already reported organocatalytic and organogelator properties. The signaling mechanism relies on the formation of a charge-transfer (CT) complex between the urea-based sensor and F¯ in the ground state with a high association constant as demonstrated by absorption and fluorescence spectroscopy. The nature of the hydrogen bonding interaction between the sensor and F¯ was established by 1H-NMR studies and theoretical calculations. Moreover, the recovery of the sensor was achieved by addition of methanol.
Multivariate Krawtchouk Polynomials and Composition Birth and Death Processes
Authors: Griffiths Robert
Published: May 2016

This paper defines the multivariate Krawtchouk polynomials, orthogonal on the multinomial distribution, and summarizes their properties as a review. The multivariate Krawtchouk polynomials are symmetric functions of orthogonal sets of functions defined on each of N multinomial trials. The dual multivariate Krawtchouk polynomials, which also have a polynomial structure, are seen to occur naturally as spectral orthogonal polynomials in a Karlin and McGregor spectral representation of transition functions in a composition birth and death process. In this Markov composition process in continuous time, there are N independent and identically distributed birth and death processes each with support 0 , 1 , … . The state space in the composition process is the number of processes in the different states 0 , 1 , … . Dealing with the spectral representation requires new extensions of the multivariate Krawtchouk polynomials to orthogonal polynomials on a multinomial distribution with a countable infinity of states.