bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacological reduction of bleeding during hip endoprosthetic replacement
Authors: de Jonge Tamás
Published: October 2012

Introduction: Endoprosthetic replacement of the large joints is accompanied by major bleeding. During the last few years several authors reported the perioperative administration of tranexamic acid and its beneficial effect on reducing the blood loss. Objectives: In the present study, the author studied the effect of intravenously administered tranexamic acid in patients undergoing primary total hip arthroplasty in order to examine whether this treatment could reduce postoperative blood loss, the amount of transfused packed red cells, and the cost of the blood saving and/or transfusion. Methods: The author compared retrospectively the data of 104 patients undergoing primary total hip arthroplasty between April, 2010 and December, 2011. 54 patients were administered tranexamic acid (Group 1) and 50 patients were treated without tranexamic acid (Group 2). The amount of postoperative bleeding, haemoglobin, hematocrit, red blood cell count, and the number of units of the transfused packed red cells were recorded. Cost effectiveness of treatment with tranexamic acid was calculated. Results: Postoperative blood loss in Group 1 was 732 ml (210–1280 ml), and in Group 2 1092 ml (420–2640 ml). Ten of the 54 patients in Group 1 had to be transfused, and the all-over need was 20 units of packed red cells. 49 of the 50 patients in Group 2 received 98 units of allogenic blood. Thromboembolic complication was not observed in connection with the use of tranexamic acid. The reduction of blood loss with the application of tranexamic acid and the transfused packed red cells cost in average 5,180 HUF per patient in Group 1 and 15,850 HUF in Group 2. Conclusions: Intravenous administration of tranexamic acid reduces effectively the transfusion rate and the blood loss in the postoperative period in patients undergoing primary total hip arthroplasty. More than 1.5 million HUF and 240 units of packed red cells could be yearly saved with the introduction of this simple, safe and cheap method of drug administered blood conservation. Orv. Hetil., 2012, 153, 1607–1612.
Vitamin D supply among healthy blood donors in County Vas, Hungary
Authors: Virágh Éva , Horváth Dóra , Lőcsei Zoltán , Kovács László , Jáger Rita , Varga Bernadett , Kovács L. Gábor , Salamonné Toldy Erzsébet
Published: October 2012

Introduction: There is growing evidence showing the importance of adequate vitamin D supply for preserving health. Aim: The aim of the study was to evaluate the vitamin D supply among healthy blood donors and healthy elderly subjects in County Vas, Hungary. Methods: Serum 25-hydroxyvitamin D, intact parathyroid hormone, calcium and albumin (Cobas, Modular, Roche), as well as serum alfa-2-globulin concentrations (Gelelfo, Interlab) were determined in 178 serum samples (68 men, 110 women, 41 were taking oral contraceptives). The results were analysed according to sex and age (younger and older than 43 years), and the impact of oral contraceptive use was also taken into consideration. Results: Deficiency and insufficiency in vitamin D levels were detected in 9.6% and 32% of the studied subjects, respectively, whereas sufficient vitamin D levels were present in 58.4% of the subjects. 63% of the older and 41.2% of the younger group had suboptimal vitamin-D supply (p < 0.01). In women taking oral contraceptives serum 25-hydroxyvitamin D and alfa-2-globulin levels were significantly higher, whereas serum albumin and calcium levels were lower than in the control group. There was no difference in serum intact parathyroid hormone concentration between oral anticoncipient users and non-users. Conclusions: The occurrence of suboptimal vitamin D supply is significant, although less frequent than that in literature reports. In women taking oral contraceptives, serum 25-hydroxyvitamin D levels were higher, but serum intact parathyroid hormone concentrations were not decreased suggesting that the increased 25-hydroxyvitamin D levels may be the consequence of oestrogen-induced alterations of serum protein fractions. Orv. Hetil., 2012, 153, 1629–1637.
Pedagogical imperatives in the teaching of project management
Authors: Ojiako Udechukwu , Chipulu Maxwell , Ashleigh Melanie , Awinda Kenneth , Samwinga Victor , Brown David , Maguire Stuart
Published: October 2012

This research builds on previous work conducted within the area of professional civil engineering education that explores pedagogical implications of teaching project management within the civil engineering discipline. The focus is to explore how pedagogical considerations impact on the experience of civil engineering students studying project management. This exploration utilises data gathered from a survey of 410 management and civil engineering students studying project management across four UK universities. Data analysis was conducted using a combination of exploratory data analysis, three-way multidimensional scaling and property fitting. Although differences in salience were found, the existence of common dimensions of project management pedagogy suggests two important implications: first that project management is independent of specific discipline peculiarities (and by implication, interdisciplinary), and second that the approach to teaching should take into account the context within which civil engineering students operate.
Reducing Fracture Propagation During the Drilling Process by Altering Wettability
Authors: Quintero Lirio , Brege Jonathan J. , Christian Chad F. , Clark David E.
Published: October 2012

While drilling through pressure-depleted formations, drilling-induced fracturing often occurs. Fracturing results when the drilling fluid overburden pressure exceeds the fracture pressure of the rock, initiating fractures that may further propagate as overburden pressure is increased. The growth in the aperture of these fractures results in lost circulation incidents. The consequences pose a major economic and safety risk when drilling. Numerous papers have been published on the concept of maximizing the fracture width to preserve the resulting hoop stress around the wellbore and effectively decrease drilling fluid losses. Using these techniques to control lost circulation with bridging materials can be extremely difficult when drilling with non-aqueous, oil-based fluid. The reduced permeability of an oil-wet filter cake prevents carrier fluid leak-off and necessary solids concentration. The resulting lower-strength plug in the fracture prevents effective support. The fracture then closes, preventing maximum hoop compression of the wellbore.

Altering the oil-wet solids in the fracture to water-wet conditions increases the ability for pressure to leak-off in fractures when placing bridging agents. This capability is paramount to improving bridging agent placement and increasing the effective strength of the wellbore. A lost circulation pill system has been developed that alters the wettability of the fracture from oil-wet to water-wet. This pill system penetrates and water-wets oil-containing fractures and enables fast pressure leak-off and fracture support, effectively increasing pressure required for fracture growth. Laboratory and chemical methods are presented that show the system is effective over a broad range of temperatures and differential pressures.
Subsea Processing in Remote Marginal Fields
Authors: Vichitrananda Vatanyoo , Simms Nigel , Sumner Joy
Published: October 2012

With ever increasing energy demands and the depletion of hydrocarbon resources, marginal fields play an important role in oil and gas exploitation. Flow assurance issues, including wax and hydrate formation, can be found in long distance tiebacks. Subsea processing, where processing equipment is installed on the seabed, can be used to solve these flow assurance issues in remote marginal fields. Subsea processing is the leading edge technology for unlocking production from reservoir under complex conditions. This paper demonstrates the opportunities in marginal field development, and analyses the implication of applying subsea processing in remote marginal fields.

The marginal field case study concerns a development with an 80 km tieback, having reserves of 120 million barrels of oil and in water 3,000 m deep in the Gulf of Mexico. The technical and economic aspects of two field development options, one employing subsea separation and boosting, and the other, an electric trace heated pipe-in-pipe flowline and subsea boosting, are compared. Hydraulic analysis of three phase flow (oil, gas, and water) using state of the art simulation software (OLGA) is performed to demonstrate production fluid behavior inside the flowline. Life cycle cost, combining both economic (CAPEX and OPEX) and risk factors (RAM), are used as the selection criterion.

Subsea separation with continuous hydrate inhibitor injection can prevent flowline blockage over the field life, while the electric trace heated pipe-in-pipe option may require subsea boosting to override the large pressure drop in late field life. In the analysis, subsea separation shows potential life cycle cost savings of up to 13% compared to electric trace heated pipe-in-pipe, indicating it may be the appropriate option when developing fields with these specific conditions. Improvement of subsea processing requires more compact designs for deepwater applications, which will help reduce both capital investment and intervention cost.
Cement Failure Probability under HPHT Conditions Supported by Long Term Lab Studies and Field Cases
Authors: Yuan Zhaoguang , Al-Yami Abdullah S. , Schubert Jerome , Teodoriu Catalin
Published: October 2012

Cement durability is very important to maintain proper well isolation and stability under HPHT conditions. In the process of well completion and production, pressure decline and temperature variation with time can contribute to cement failure and wellbore stability issues. However, there is no available investigation in the durability and comparison of different types of cement at higher temperature and at different operational scenarios.

Three different types of cement (72 pcf, 101 pcf and 118 pcf) commonly used in the Middle East were cured and tested at 300°F in the study. The tests included one year mechanical properties measurement such as compressive strength development, Young's modulus and Poisson's ratio.

Finite element method was used to analyze the failure probability of HPHT wells over with time. At the variation of bottom hole pressure and temperature, the casing, cement, and formation system failure probability was studied for these types of cement. The results show that the pressure variation has more effect on the wellbore stability than the temperature variation for HPHT wells. Low density cement can improve the wellbore stability issues due to the cement elastic behavior.

This paper introduces the operational envelope for every type of cement investigated in order to achieve successful operations based on field conditions. Field cases were discussed to validate the results of this investigation.
Prediction of Liquid Loading in Gas wells
Authors: Nallaparaju Yashaswini Devi
Published: October 2012

It is a well known fact that the hydrocarbon demand increases by the day. Now, in order to meet this ever increasing demand it is essential for us to produce at the required rate over a specified period of time. The most prominent problem affecting production in gas wells is Liquid Loading. It is basically the inability of gas to remove liquids being produced in the wellbore. This occurs when the velocity of gas being produced falls down a particular value known as "critical velocity". The produced liquid will accumulate in the well creating a static column of liquid, therefore creating a back pressure against formation pressure and reducing production until the well ceases production. This problem should be predicted early and dealt properly to prevent economic losses and produce efficiently.

Some notable correlations that exist for predicting the critical rate required for liquid unloading in gas wells include Turner et al., (1969), Coleman et al., (1991), Nosseir et al. (1997) and Li et al. (2001). However, these correlations offer divergent views on the critical rates needed for liquid unloading and for some correlations in particular, at low wellhead pressures below 500 psia. In this paper, we compared the critical velocity graphs obtained from different models for four different wells and concluded that Turner model gives the most conservative value of critical velocity of all the methods for any value of pressure. The turner model is most widely used and accepted in oil and gas industries and moreover all the theories are based on the Turners model.

Using Nodal Analysis we integrated IPR and TPR curves to find out the operating point of the wells. Then by intersecting turner model curve with the future IPR curves we predicted the year in which the problem of liquid loading may occur. This will help us in taking necessary precautions beforehand.

After liquid loading has occurred, there are different deliquification techniques to deload the well. They have been presented in this paper, which help in reinitiating gas production.
Responsible Oil Well Tests on Artificial Islands Close to Offshore Waters
Authors: Dhufairi Mubarak , Arukhe James , Mutairi Saleh , Ghamdi Saleh , Aborshaid AbdulHameed
Published: October 2012

Safeguarding and restoring the normal ecosystems and environment of the Arabian Gulf in an active hydrocarbon province undergoing field development is a tough challenge. Nevertheless, a multidisciplinary team involved in this field development has maintained a profound commitment in stewarding natural resources of the major carbonate field in Saudi Arabia.

As part of the Kingdom's strategy to maintain crude oil production targets, production tests were needed to confirm potential of the wells in the Southern part of the field's structure prior to commissioning. The wells are located on drill sites in some artificial islands that were reclaimed from the sea. The six-well deliverability testing campaign should greatly enhance offshore field development, help to obtain reservoir characterization parameters, evaluate stimulation needs for producers, and assess comingling concept for selected wells. A total of 27 artificial Islands and a major transportation causeway were constructed by land reclamation from offshore waters of the Arabian Gulf. These facilitate onshore access to drill sites thus eliminating relatively more expensive fixed steel jacket rigs or platforms.

Due to land space limitation and well spacing constraints on the drill sites, a compact well test facility layout was specifically designed to achieve smokeless flaring, full combustion, and minimize environmental impact. The design consists of two heat exchangers, three-phase separators, i-loop systems for effective H2S scavenging and chemical mix with crude, surge tanks and air compressors. When deployed, this system helped to meet the test objectives and addressed space limitation challenges, mitigated risk to sea pollution in a sensitive marine environment, and forestalled uncontrolled release of hydrocarbons to the environment.

The completion of the cleanup and flow back operation on these wells with no single safety incident, uncontrolled release of hydrocarbons, or spill to nearby offshore waters was a major demonstration of leadership and a key contribution to well testing in similar environments.
Integrated Dynamic Flow Analysis to Characterize an Unconventional Reservoir in Argentina: The Loma La Lata Case
Authors: Badessich Matías Fernandez , Berrios Vicente
Published: October 2012

In November 2010 YPF brought online the very first shale oil well in Argentina in the northern area of Loma La Lata field after successfully fracturing the Vaca Muerta formation, the main source rock in the Neuquen basin. Initial choked productivity exceeded 250 bopd of high quality oil from an average depth of 9,500 ft. Since then, YPF has pioneered a new era of production from unconventional reservoirs in Argentina with many more wells coming onstream.

As it is well known, production forecasting and reserves estimation in this kind of reservoirs is fraught with challenges and pitfalls. Many methods have been applied so far; these range from very simple decline curve analysis to highly elaborate reservoir simulation models.

In order to understand and monitor the production behaviour of the YPF wells, several reservoir and production analysis techniques have been applied such as pressure transient analysis, rate transient analysis, interpretation of available DFITs and time-lapsed production logging measurements.

In this paper we present what YPF has implemented as a robust workflow for analyzing dynamic data that captures the physics of the flow process, explains the observed data and provides a method for forecasting reserves for a range of assumed in-place volumes.
Optimization of Gravel Pack Techniques in Baram South Using a Statistical Tool
Authors: Hatta Siti Aishah , Jadid Maharon , Saaid Ismail M
Published: October 2012

Baram field is a mature oil field in Sarawak, Malaysia and it is the largest and most structurally complex field in the Baram Delta Province. The reservoirs are thinly stacked and predominantly friable and unconsolidated requiring active sand control by gravel packing techniques being the most reliable sand control method available. Sand production in Baram wells resulted in several wells being shut-in, low oil production and costly surface maintenance to remove the sand. The drawbacks of gravel packing techniques were its high wellbore skins due to gravel carrier fluids, intermixing of gravel and fine sands, and blockage of gravel filter bed from fines migration over time resulting in lower well PIs and flow efficiencies through the gravel pack (GP) completions.

This paper reviews the gravel packing techniques applied in 47 completions in Baram South with the aim of identifying the most optimum method for gravel packing in future Baram South wells. A statistical tool called Taguchi Method for Design of Experiment and Analysis of Variance (ANOVA) were employed to analyze impact of the well deviations, gravel packing techniques and permeability variation on skin factor. It is a simple and reliable tool to analyze extensive amount of data and introduces the signal-to-noise ratio as an indication of effect each variable has on the output (skin). The statistical study concluded that the most suitable gravel packing technique for Baram South is High Rate Water Frac (HRWF). The GP technique adopted appears to be the dominant factor contributing to the skin while the type of reservoir and the deviation of the well have minimal effect.
Coiled Tubing Long Perforation CIRP with Live Correlation GR/CCL Application via Optical Telemetry: A Success Story at Angsi Field, Malaysia
Authors: A. Jalil M. Izwan , Ooi Zhon Wei , Kasim M. Heikal , Ishak M. Fakhrurazi
Published: October 2012

Angsi is one of the major fields in PETRONAS Carigali Sendirian Berhad. Located at offshore Terengganu in the Malay basin area, Angsi has become the top priority in terms of oil and gas production. A33L was producing intermittently through low-pressure system. Due to its rapid production decline, decision was made to restore its potential by adding perforations via Coiled Tubing.

Since adding perforations could be challenging due to the complexities such as on-depth perforation, depth accuracy of Coiled Tubing and uncertainty of depth correlation prior to detonation, fibre optic-enabled Coiled Tubing was chosen to convey the perforating guns. The job, planned to perforate I-95 and I-100 sand would require 120-ft of future perforations interval; was performed with an under pressure deployment system namely Completion Insertion and Retrieval under Pressure (CIRP). CIRP enables long perforating guns to be deployed in a single run and the combination of live correlation Gamma Ray and Casing Collar Locator via fibre optic-enabled Coiled Tubing; multiple perforating runs were avoided specifically for this well.

As a result, the well is currently producing 50 MMscf/day and with the success of this operation, it is anticipated that by combining several key technologies for this kind of job will not only ensure high level of perforating accuracy but also economically acceptable considering the value creation by the job.

This paper will discuss in detail the complexity of the overall operation, well challenges and the extended jacking frame built to accommodate the operation. Futhermore, the gun insertion, deployment and retrieval as well as live correlation via optical telemetry through coiled tubing will also be elaborated. The decision making process and well intervention equipment selection throughout the overall job operations will also be highlighted.
An Innovative Processing Method for High Resolution LWD Density Images in Water and Oil Based Mud
Authors: Li Jing , Kennedy David , Dawber Mike , Lee Rick , Boonen Paul , Hollmann Joseph
Published: October 2012

With the rapid growth of horizontal drilling, azimuthal LWD bulk-density images (and also photo-electric effect images) have proven to be indispensable tools for the identification of bed boundaries, estimating bed dips, and determining the steering direction of the drilling assembly. The inherent low resolution of the density measurement has, however, typically limited the interpretation of these images to the analysis of structural scale features. The ability to image finer scale detail is governed to a large extent by sampling density.

Sampling density depends upon the sampling frequency of the instrument, the rate of penetration of the drilling assembly and the rotary speed of the drillstring. Conventional downhole image processing schemes average raw measurements either in time or depth before sectoring them into relatively large circumferential sectors. This averaging process conserves tool memory and smooths noisy data but inevitably results in the loss of high spatial frequency instrument responses associated with fine scale geological features. Instead of compressing data, we present a method that preserves all the raw measurements stored in the tool memory and maps them to a grid around and along the borehole. Statistical noise is mitigated and a specially designed interpolation scheme is used to fill empty grid locations before analyzing the data and smoothing the results. This methodology allows the creation of high resolution images with up to 256 circumferential sectors and a depth increment as small as 0.6 inches.

The technique is equally applicable to borehole image data acquired by any type of logging tool providing that the raw measurements are frequently sampled and stored in the tool memory. For example, high resolution borehole caliper images have also been created from ultrasonic transducer measurements of the same tool used to acquire the data presented in this paper. Azimuthal bulk-density data acquired in this manner allows for the opportunity to produce optimized images in oil-based mud and overcomes the limitations of LWD micro-resistivity imaging tools in non-conductive borehole fluids. This technique has been successfully applied to wells drilled in both the UK North Sea and US land. Field examples presented in this paper illustrate the benefits of the application in imaging thin beds, sedimentary bedding structures, coal seam bedding internal structure, faults and fractures.
Impact of Material Balance Equation Selection on Rate-Transient Analysis of Shale Gas
Authors: Williams-Kovacs J. D. , Clarkson C. R. , Nobakht M.
Published: October 2012

Various forms of shale gas (SG) material balance equations (MBE) have been developed in the past several decades, dating back to the first round of coalbed methane (CBM)/SG development in North America. These equations attempt to incorporate various aspects of SG storage mechanisms and reservoir characteristics; simple to complex forms exist, depending on the number of assumptions made in their derivation. All of the equations account for adsorbed gas storage, but may or may not include corrections for pore volume (PV) and fluid compressibility, water influx etc. In higher-permeability fractured SG and CBM plays, application of material balance using static (shut-in) pressures to derive original gas-in-place (OGIP) and drainage area estimates has proven useful. With the current development of ultra-low permeability SG (and shale liquids) plays, shut-in times for wells is impractically long so as to preclude the use of static material balance (SMB) methods. Use of rate-transient analysis (RTA) techniques, such as the flowing material balance (FMB), is much more common for original gas-in-place (OGIP) derivations in ultra-low permeability reservoirs, yet some form of MBE is often required for application of these methods. For example, pseudo-time and material balance pseudo-time is commonly used in advanced RTA methods, and hence the form of MBE could impact reservoir and/or hydraulic fracture properties derived from the analysis.

In this work, we first summarize the MBEs that have been derived specifically for SG and/or CBM, with an emphasis on the assumptions, limitations and applications of each equation. We then derive a new MBE that dynamically adjusts free-gas storage volume during depletion according to the amount of volume occupied by sorbed gas, as recently suggested by Ambrose et al. (2010) for volumetric gas-in-place determination. Finally, we examine the impact of MBE selection on quantitative rate-transient analysis (for estimation OGIP). Two simulated cases for SG reservoirs are used to demonstrate the impact of the selected MBE. Finally, a modified transient productivity index (PI) using average pressure in the region of influence was developed and is compared to conventional transient PI. The results of this study are of interest to those engineers performing unconventional reservoir characterization work using RTA and for reserves estimators.
Characterization of Critical Fluid, Rock, and Rock-Fluid Properties-Impact on Reservoir Performance of Liquid-rich Shales
Authors: Honarpour M. M. , Nagarajan N. R. , Orangi A. , Arasteh F. , Yao Z.
Published: October 2012

Liquid-rich Shale (LRS) reservoirs are economically attractive but operationally challenging. Fluid, rock, and rock-fluid properties are critical for optimal reservoir development and management. Formation heterogeneity, fluid variability, and complexity of rock-fluid properties render fluid flow characterization a challenging task. Additional challenges associated with coring, fluid sampling and analysis include the recovery of quality cores and representative fluid samples, and timely acquisition of high quality data for making critical engineering design decisions.

Rock and fluid analyses should be done in the following stages so that the critical data become available in a timely manner for making key decisions:

a) ‘Wellsite Analysis’ including mineralogy/total organic content, TOC; b) ‘Quick Look laboratory analysis’ for detailed mineralogy and basic petrophysical properties; c) ‘Fast Track’ geomechanical, geochemical properties and petrophysical analysis on core plugs; and d) ‘Full Suite’ rock-fluid analysis for integrated studies.

Low formation permeability, long transients, and contamination with OBM and fracturing fluid make acquisition of representative downhole or early surface fluid samples impractical. An alternative approach is to integrate mud gas analysis with light and heavy end components extracted from full diameter cores in canisters to reconstruct in-situ fluids. The PVT modeling should account for the impact of high capillary pressures encountered in unconventional shale reservoirs for reliable reservoir performance prediction.

This paper presents the best practice methodology for characterizing critical rock and fluid properties, their variability and their impact on performance through parametric simulation studies. A sector model was constructed consisting of alternate TOC- and calcite-rich layers with a horizontal well placed in a calcite-rich layer. A network of hydraulic and natural fractures was implemented in the model to study the sensitivities to fluid and rock properties, relative permeability, capillary pressure, and fracture properties. It was found that the critical rock and fluid data impacting the initial rate and ultimate recovery were effective permeability, its anisotropy, its alignment with hydraulic and natural fracture network, rock-type based compaction, unconventional PVT behavior such as decreased oil bubble point pressure and the resultant viscosity and GOR behavior, interfacial tension (IFT)/capillary pressure, and relative permeability.
The Effect of Water-Induced Stress to Enhance Hydrocarbon Recovery in Shale Reservoirs
Authors: Fakcharoenphol Perapon , Charoenwongsa Sarinya , Kazemi Hossein , Wu Yu-Shu
Published: October 2012

Waterflooding has been an effective improved oil recovery process for several decades. However, stress induced by waterflooding has not been well studied or documented. Water injection typically increases reservoir pressure and decreases reservoir temperature. The increase in reservoir pressure and decrease in reservoir temperature synergistically reduce the effective stress. Because of such decrease in stress, existing healed natural fractures could be reactivated and/or new fractures could be created. Similar effects could enhance hydrocarbon recovery in shale reservoirs.

In this paper, we calculated the magnitude of water injection-induced stress using a coupled flow-geomechanics model. To evaluate the effect of water injection in the Bakken, a numerical simulation study for a sector model was carried out. Stress changes due to the volume created by the hydraulic fracture, water injection, and oil production were calculated. Hoek-Brown failure criterion was used to compute rock failure potential.

Our numerical results for a waterflooding example show that during water injection, the synergistic effects of reservoir cooling and pore-pressure increase significantly promotes rock failure, potentially reactivating healed natural macrofractures and/or creating new macrofractures, especially near an injector. The rock cooling can create small microfractures on the surface of the matrix blocks. In shale oil reservoirs, the numerical experiments indicate that stress changes during water injection can improve oil recovery by opening some of the old macrofractures and creating new small microfractures on the surface of the matrix blocks to promote shallow water invasion into the rock matrix. Furthermore, the new microfractures provide additional interface area between macrofractures and matrix to improve oil drainage when using surfactant and CO2 EOR techniques. These positive effects are particularly important farther away from the immediate vicinity of the hydraulic fracture where much of the undrained oil resides.
Dynamic UnderBalance perforations bring higher productivities than conventional perforations: a large scale comparative review from the Tunu Gas Field (Indonesia)
Authors: Perrier Sebastien , Sugiarto Tomi
Published: October 2012

Tunu is a multilayered gas field operated by Total EP Indonesie in the Kutei basin, which has produced 8Tcf since 1993. It consists of thousands of gas-bearing sandstone reservoirs, spread over up to 2000m of vertical gross thickness, developed using tubingless completions (more than 700 wells to date). Perforations are performed by light electric unit swamp barges, following a progressive bottom-up strategy.

Perforation techniques applied in the field typically involve perforating in static under-balanced pressure conditions with conventional guns and charges (underbalance value and gun design may vary). However, more than 40 reservoirs were perforated using Dynamic Underbalance technologies between 2005 and 2011.

This paper presents an in-depth comparative survey of the performance of these 2 perforation techniques, and compares the productivity obtained from these jobs to an extensive benchmark of documented conventional perforations.

Methodologically, all reservoir and perforation parameters influencing perforation performance are reviewed, to search for, and correct, any possible statistical bias in the comparison of different groups of reservoirs. Using methods classically used in epidemiological statistics, the aim is to get a statistically sound comparative survey on the productivity provided by these two techniques of perforation.

Based on two independent methods, this paper shows that the Dynamic Underbalance technique provides reservoir productivities significantly better than conventional perforations in gas reservoirs. The robust statistical confidence associated to this productivity increase will be explicitly discussed and presented in this paper.
Transient Pressure Test Interpretation for Continuously and Discretely Fractured Reservoirs
Authors: Kuchuk Fikri , Biryukov Denis
Published: October 2012

Fractures are common features of many well-known reservoirs. Naturally fractured reservoirs consist of fractures in igneous, metamorphic, and sedimentary rocks (matrix) and formations. Faults in many naturally fractured carbonate reservoirs often have high permeability zones, and are connected to many fractures with varying conductivities. Furthermore, in many naturally fractured reservoirs, faults and fractures can be discrete (i.e., not a connected-network fracture system). To understand the pressure behavior of these continuously and discretely fractured reservoirs, semianalytical solutions are presented. These solutions are used for transient well test interpretation of formations containing a network of discrete and/or connected (continuous) finite- and infinite-conductivity fractures. In this paper we present an extensive literature review of the pressure transient behavior of fractured reservoirs. First, we show that the Warren and Root (1963) dual-porosity model is a fictitious homogenous porous medium because it does not contain any fractures. Second, using the new solutions, we show that for most naturally fractured reservoirs the Warren and Root (1963) dual-porosity model is inappropriate and fundamentally incomplete for the interpretation of pressure transient well tests because it does not capture the behavior of these reservoirs.

We examined many field well tests published in the literature. With few exceptions, none of them shows the behavior of the Warren and Root (1963) dual-porosity model. These examples exhibit the very rich pressure behavior of discretely and continuously fractured reservoirs. Unlike the single derivative shape of the Warren and Root (1963) model, the derivatives of these examples exhibit many different flow regimes depending on fracture distribution, and on their intensity and conductivity. We show these flow regimes using our new model for discretely and continuously fractured reservoirs. These derivatives will be a valuable diagnostic tool for well test interpretation. Most well tests published in the literature do not exhibit the Warren and Root (1963) dual-porosity reservoir model behavior. If we interpret them this dual-porosity model, then the estimated permeability, skin factor, interporosity flow coefficient (λ), and storativity ratio (ω) will not represent the actual reservoir parameters.
Real-Time Prediction Ahead of the Bit in an Exploration Well in the Cordillera Basin, Colombia
Authors: Duque Helman , Ramirez Carlos Andres , Quinn Dan , Rodriguez Yerayen , Jaramillo Jose Arturo , Ruiz Juan Camilo
Published: October 2012

New areas of oil exploration in Colombia are usually located in complex geological settings where conventional surface seismic data is traditionally of poor resolution. The recent improvements in borehole seismic software applications has made it possible for real-time vertical seismic profile (VSP) processing at wellsite to provide time-critical information with improved vertical resolution. This advancement has promoted the use of VSP applications in complex areas, as is the case of the zero-offset vertical seismic profile (ZVSP) data that was acquired in an exploration well in the Cordillera basin of Colombia. The real-time results obtained by processing the VSP data at the wellsite shortened the decision-making process (reduced NPT); in this case, it aided in the decision to invest additional resources to continue to drill a reflector observed on the VSP below the initial target. This case history describes the real-time wellsite application of acoustic impedance inversion of the upgoing waves and prediction ahead of the bit. In this example, the new target was encountered 5 ft below the prediction. The acquisition and processing of this data reduced uncertainties and verified the new target below the bit.

The results of the theoretical model and the actual data demonstrate that the method is effective for pre-drilling predictions using borehole seismic data; these results also make the VSP a powerful tool for making decisions during the drilling stage of the project. This paper describes the acquisition, processing, and method used to help improve subsurface imaging and to predict the depth to the reflectors ahead of the bit.
Application of CFD to Debottleneck Production Separators in a Major Oil Field in the Middle East
Authors: Kharoua Nabil , Khezzar Lyes , Saadawi Hisham
Published: October 2012

In order to debottleneck very large three phase production separators in a Middle Eastern oil field, new high efficiency internals were installed. A Computational Fluid Dynamics (CFD) study was conducted of these three-phase separators. The study focused on the evaluation of internal modifications and the influence of the inflow characteristics. A combination of the Eulerian-Eulerian multiphase and k-ε turbulence models was used to simulate the complex behavior of the flow inside the separator. A series of parametric case studies was conducted. The findings of the CFD study were compared with the results of field performance test.

This paper describes the approach adopted in the CFD study. The geometry, mesh, numerical models, simulation strategy as well as the results and findings are discussed in detail.
An Examination of Cultural Values and Employees' Perceptions of Support on Affective Reaction and the Desire to Participate in a Formal Mentoring Program in an OilField Services Corporation
Authors: Hayes Hanna Bea , Rousseau Meta
Published: October 2012

Many researchers have examined the effect of formal mentoring on job satisfaction and organizational commitment. However, there has been little or no focus on an employee's intent to participate in a formal mentoring program based upon an employee's perceived organizational support, and/or affective reaction (job satisfaction and organizational commitment). In the current study, the researcher examined the relationship among cultural values, perceived organizational support (career and psychosocial support), affective reaction (job satisfaction and organizational commitment), and the intent to participate in a formal mentoring program in an oilfield services organization. A 44-item electronic survey was utilized to collect data. The questionnaire was sent to 831 Field Engineers 1 (FEl's) in forty-two countries within an oilfield services organization. The sample included 341 respondents. Descriptive statistics, Cronbach's alpha estimates for reliability, factor analysis, correlation analysis, regression analysis, path analysis, and structural equation modeling were the analyses used in the study.

The researcher posited that cultural values amongst the FEls do not differ significantly; moreover, the cultural values do not influence the FEls perceived organization support. Further, it was found that FEl's perceived support (career and psychosocial) and affective reactions predicted the FEl's intent to participate in a formal mentoring program.
Advanced Completion and Fracturing Techniques in Tight Oil Reservoirs in Ordos Basin: A Workflow to Maximize Well Potential
Authors: Liu Hai , Luo Yin , Li Xianwen , Xu Yonggao , Yang Kewen , Mu Lijun , Zhao Wen , Zhou Shuxun
Published: October 2012

In recent years, great efforts have been focused on tight oil reservoirs in Ordos Basin, which is located in North Central China. Although historical field development in these tight oil reservoirs was still economical, average production after hydraulic fracturing is quite low and most of wells produce just at the margins. In order to understand production potential through appropriate completion and fracturing techniques, a pilot project was initiated recently on two horizontal wells drilled in parallel, with three vertical wells placed between two horizontal wells along the lateral for real time fracturing monitoring.

This paper describes how the treatment design was optimized based on detailed formation evaluation and fracture simulation using a 3D unconventional fracturing design workflow. It presents real time fracture mapping results through a dual monitoring well setup on total 26 stages of fracturing treatments, and also illustrates how the results were utilized to adjust and optimize treatment design during and between treatment stages. The paper demonstrates the application of a unique Unconventional Fracture Model (UFM) that was developed for design and evaluation hydraulic fracturing treatment in unconventional reservoirs. The model incorporates predefined natural fracture patterns and interaction criteria for hydraulic and natural fractures. The paper also discusses the outcome of simultaneous treatments tested in four stages compared to other stages pumped in sequences.

Initial production tests on both wells show 124.5 m3/d and 103.2 m3/d respectively, which are significantly higher than all the wells completed in tight oil reservoirs in the basin, of which the production varies from 5-8 m3/d in vertical wells to 32 m3/d in horizontal wells on average. In-depth reservoir understanding, advanced design and evaluation workflow, and appropriate completion and fracturing technique are the key of this success, which has set a milestone for developing such tight oil reservoirs in Ordos Basin.
Strategic Baseline Groundwater Sampling for Shale Exploration
Authors: Leatherbury Ryan , Denson Barbara Brandl
Published: October 2012

Exploration and production from unconventional shale resources has increased significantly in the past several years due to the success of combining horizontal drilling and hydraulic fracturing technologies in a manner that allows natural gas and/or oil to be released from relatively impermeable shale formations. The rapid increase in shale development has raised the concern of landowners and the public that the use of these techniques could adversely impact the groundwater resources in and around the development. In general, there is a lack of real data documenting pre-drill and post-drill conditions that could be used to truly evaluate the impacts of shale development. Using a technically sound strategy to collect data is important in an effort to document baseline environmental and, in particular, groundwater conditions prior to exploration so that post drilling conditions can be evaluated when necessary. The collection of scientifically defensible data for operators involved in the development of a shale play improves stakeholder engagement, protects operators from potential environmental degradation claims, and allows for science-based regulation that truly protects the resources. Collecting a representative set of samples from groundwater supply wells within a defined radius of a well pad prior to drilling activities provides the operator with information that documents pre-drilling groundwater conditions. Performing this type of baseline sampling within a well-designed, scientifically and legally defensible program can help the operator manage and mitigate corporate risk. The public concern over impacts to groundwater must be taken seriously, and adhering to a well designed program that produces science-based results will increase public confidence in the industry's operating practices. This paper presents baseline groundwater sampling program rationale and design based upon existing regulations and experience gained in the United States shale exploration regions.
Challenges of Heavy Oil Fluid Sampling and Characterization
Authors: Nagarajan N. R. , Dong C. , Mullins O. C. , Honarpour M. M.
Published: October 2012

A significant portion of the world's hydrocarbon reserves is found in heavy oil reservoirs. Heavy oils are often found in shallow and highly unconsolidated reservoirs, or sometimes in deep, tight formations. Often the high asphaltic content of these oils results in relatively higher oil density and viscosity; hence, their lower reservoir mobility poses significant challenges to both sampling and PVT data measurements. Furthermore, modeling these fluids for reservoir evaluation requires special techniques to capture their unique phase behavior.

The challenges of representative down-hole or surface fluid sample acquisition demand customized sampling methods to deal with:

low oil mobility sand production from unconsolidated formations high asphaltene content and resulting high gradients formation of water-in-oil emulsion during co-production of water or gas lift operations or addition of diluents

In addition, the prerequisite for laboratory measurement is special sample preparation to remove emulsified water. These high viscosity oils exhibit slower gas liberation below the bubble point and hence delayed gas-phase formation, thus making "true" oil property measurements a challenge. Difficulties associated with fluid modeling include characterizing apparent bubble point behavior, large viscosity changes with pressure and temperature, and asphaltene dropout.

In this paper, we present a comprehensive methodology for heavy oil sampling and characterization in unconsolidated sands as well as in low permeability reservoirs. We present field examples to highlight the challenges and illustrate the methodology for fluid sampling, down-hole fluid analysis, laboratory PVT data acquisition, and modeling. Sampling methods for heavy and asphaltic oils were custom designed with special tools and sensors to obtain representative samples and precise down-hole fluid analysis data. New laboratory techniques were developed to prepare the samples for analysis and to distinguish between the "true" and "apparent" bubble point behavior exhibited by the heavy oil due to its non-equilibrium behavior. Fluid models based on a special equations of state (EoS) were employed for accurate description of heavy oil fluid phase behavior. In particular, we successfully applied the industry's first EoS for asphaltene gradients in heavy oil reservoirs that match down-hole fluid data.