bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Security on Offshore Installations
Authors: Struthers Donald , Esson George , Ferguson Ronald 
Published: December 2007

Abstract
"Improving Security On Offshore Installations"
Without question, the offshore oil and gas industry is vitally important to the global economy. It is an industry that operates worldwide, often in what is described as ‘hot spots’ or high-risk areas. Therefore it is clearly essential to ensure robust measures are in place to safeguard the industry's assets and people against unlawful acts, be these attacks of terrorism or from any other form of criminality. Achieving that leaves no room for complacency; therefore "Improving Security On Offshore Installations" should be a clear objective of all involved in the industry.
Prediction of Permeability Reduction Rate Due to Calcium Sulfate Scale Formation in Porous Media
Authors: Tahmasebi H. A. , Kharrat R. , Masoudi R. 
Published: December 2007

Abstract
Water injection is usually associated with various types of mineral scale formation and deposition which significantly undermine the performance of the injection by changing some reservoir properties such as permeability and porosity. Mineral scale deposition in surface and subsurface petroleum streams is one of the main concerns affecting the economy and safety of any production scenarios.
Among various types of mineral scales, calcium sulfate is one of major scales in petroleum industry that can cause sever flow assurance and formation damage issues. Many parameters are affecting this problem. Temperature, pressure, fluid concentration, ratio of brine to hydrocarbon, fluid dynamic and type of porous media are among these parameters. Interpretation and prediction of permeability reduction in such complicated system is very complex.
In this work an experimental and theoretical study has been conducted to investigate the permeability reduction due to CaSO4 scale formation. For this purpose, brine solutions containing calcium and sulfate ions were injected in a packed glass beads porous media at elevated temperatures and various flow rate and brine concentrations. The pressure decline and permeability changes were measured in all the conducted tests. It was found that the permeability reduction by calcium sulfate scale formation follows a systematic trend considering various above mentioned important parameters. Hence, a novel empirical equation has been suggested, which can predict permeability reduction rate with high accuracy to experimental data.
Incorporating Multiphase Behaviours in Dynamic Simulation Models Using in-Situ-Generated Pseudofunctions
Authors: Al-Busafi Bader , Al-Siyabi Zaid , Fisher Quentin 
Published: December 2007

Abstract
This work presents the use of pseudoisation to account for faults using practical representations of the multiphase behaviour of fault rocks within production simulation models The work starts by revisiting the conventional representation of fault sealing capacities in simulation models using transmissibility multipliers (TMs). TMs, as proposed by Manzocchi et al. (1999) are absolute and phase-independent values that are used to take into account the presence of fault-rocks within production simulation models and are calculated based on the fault thickness and absolute permeability, as well as the size and properties of the undeformed grid-blocks adjacent to faults. The crucial limitation of TMs is that they do not take into account the multiphase behaviour of fault rocks, whose relative-permeability and capillary-pressure curves can have very different characteristics to their juxtaposed host-rock curves.
This paper presents and tests a practical representation of the multiphase behaviour of fault rocks within production simulation models using in-situ-generated pseudofunctions. The generated dynamic pseudofunction curves are attached to the upstream cells of the faults using an analogous method to that proposed by Manzocchi et al. (2002). This method takes into account in-situ fractional flows and compartmentalised phase pressures across fault faces between non-neighbour connections. The proposed method gives very promising results when applied to a 3-D, two-phase model with fault-rock thicknesses ranging between 0.5 and 3 ft, and typical fault rock permeabilities (0.1-0.01) mD
Wettability Evaluation of the Unayzah Reservoir in Central Saudi Arabia
Authors: Okasha T. M. , Al-Saleh S. H. , Al-Khudair W. S. 
Published: December 2007

Abstract
Unayzah Formation in Central Saudi Arabia is an important source of light (48-52 API gravity) sulfur frees (0.02-0.07%) crude oil (Arabian Super Light). In 1989, the first oil discovery was made at Hawtah. Subsequently, a number of other oil discoveries were made at various fields (Umm Jurf, Ghinah, Nuayyim, Hazmiyah, etc.). Oil production from Central Saudi Arabia fields started in August 1994. As part of special core analysis program to support reservoir management in development of these fields, intensive SCAL studies were completed and crucial data required for field simulation were provided to proponents.
This paper summarizes the results of a set of consistent methods used in determining wettability of Unayzah reservoir. Both quantitative methods (Amott, USBM, and contact angle) and qualitative method (oil/water relative permeability) were used to evaluate the variation of wettability in Central Saudi Arabia fields. In this work, direct wettability tests were carried out on a large number of native core plugs from Unayzah reservoir. Moreover, several waterflood tests were conducted at reservoir conditions on composite cores using recombined reservoir fluids. Data from relative permeability curves were used for comparison with wettability results obtained from direct wettability tests.
Amott and USBM wettability indices indicated that Unayzah reservoir core material represented a range of wettabilities, but tended towards neutral to slightly to strongly water-wet. Contact angle results for rock material recovered from Unayzah reservoir showed water-wet characteristics for both oil-brine/rock system and oil-brine/quartz system. Moreover, the values of wettability indices are in agreement with relative permeability results which reflect a behavior of water-wet core material based on Craig's rule of thumb.1
Striving the Coil Tubing Limit Intervention on Snake "Long Horizontal" Complex Gas Well: Successful Perforation and Completion
Authors: Al-Araimi Nasser M. , Srisa-ard Surasak 
Published: December 2007

Abstract
Well A was drilled and completed in 2004 with smart intelligent completion. Total length of the well was nearly 6000 meter; it was very long complex horizontal "snake type" section (up to 3500 meter) with a smart completion, remote control of surface Flow-Control-Valves (FCV), Inflow Control Valves (ICV) for surface controlling of production from each zone, down-hole temperature and pressure gauges for monitoring each individual zone and A hydraulically controlled down hole choke (lower/upper valve) to control the inflow.
The well was completed in all upper sand packages. The upper two zones were perforated prior ran the completion using TCP (Tubing Convey Perforation) guns on drill pipe whilst rig is on site. The lower zones were to have been perforated after the completion was run, but there were completion difficulties such as plug could not be pulled to allow access the lower completion for further well intervention and completion i.e. logging and perforation.
This paper will show coil tubing operations success and challenges in a very complex horizontal "snake" type well for perforations and completion. Also setting up a milestone of Coil tubing confront and technical limit. Also will describe the processes, engineering and job execution associated with the successful running of CT in a very complex environment and pushing the CT limit envelope. Several innovative techniques were utilized; using coiled tubing tools, hydraulic jars and hammers. Overall, this paper is intended to share the knowledge and unique experiences gained during this innovative CT perforation and completion intervention on this well, which lead to the well to produce 2-2.5 million m3/d gas and 800 m3/d condensate.
Determination of Water–Producing Zones While Underbalanced Drilling Horizontal Wells—Integration of Sigma Log and Real–Time Production Data
Authors: Gauthier P. J. , Hussain H. , Bowling J. , Edwards J. , Herold B. 
Published: December 2007

Abstract
The paper presents a novel logging approach used to identify water producing zones while under-balanced drilling (UBD) horizontal wells. This approach will work in mixed-wet reservoirs and is particularly attractive for mature reservoir undergoing waterflooding.
The logging process consists of a standard logging-while-drilling (LWD) data acquisition followed by a pulse neutron capture run (PNC). The PNC data is acquired after pumping the tool inside the drillpipe to total depth (TD). The LWD-resistivity and PNC-sigma measurements are used to calculate completely independent oil saturation curves. This additional information is important for non-water-wet reservoirs because a separation between the resistivity and sigma-derived oil saturation will indicate a flushed zone. The separation is due to what is called resistivity hysteresis and is well documented in the literature and observed in the laboratory for this reservoir.
The logging information is complemented with real-time production data which provides a pseudo-inflow log of water and oil inflow intervals along the horizontal wellbore. The pseudo-inflow log is used to validate if saturation differences correlate with water production.
The approach is made possible because the wells are drilled under-balanced meaning that, during the drilling process, the reservoir pressure is always higher than the pressure in the wellbore. This pressure differential avoids drilling fluid invasion into the formation, which is necessary for shallow nuclear logging and allows the reservoir to flow for real-time production characterization.
Results from eleven UBD wells show that a positive correlation exists between inflow of water and separation between the resistivity and sigma-derived oil saturation. This is in agreement with the resistivity hysteresis concept.
This application can become important for projects developing mixed-wet reservoirs especially during the infill drilling or waterflood phases. The PNC logging operations takes between 6 and 12 hours and can be adapted with minimal incremental cost to most UBD operations.
The Velocity Field and Pressure-Drop Behavior in a Rough-Walled Fracture
Authors: Mou J. , Hill A. D. , Zhu D. 
Published: December 2007

Abstract
The transport of fluids down a hydraulic fracture is computed in fracture models by assuming some regular shape for the fracture. In the most complex 3D fracture models, each grid block is assumed to have parallel fracture walls. However, small-scale variations in the fracture width (or wall roughness) may increase the pressure drop, alter the 3D flow field, and, in the case of acid fracturing, influence the etching pattern along the fracture walls.
An accurate prediction of acid fracture conductivity necessitates the detailed description of the acid etching profiles on the fracture surfaces, which depends on acid transport in the fracture, leakoff due to local permeability, and acid/rock reactions. Although a 3D acid fracture model can predict nonuniform etching throughout a fracture, current computational limitations result in dividing the fracture into grid blocks that are several feet to tens of feet on a side, which is much larger than the scale of local heterogeneity and channeling characteristics. We are developing an intermediate-scale acid fracture conductivity model with grid sizes of a few inches to close the gap between laboratory-scale measurements of acid fracture conductivity and macro-scale acid fracture models. The key to such a model is the convective transport of fluid through a heterogeneous fracture.
This paper presents a method to calculate the 3D velocity fields for an intermediate-scale acid fracture model. Incompressible steady-state 3D Navier-Stokes equations describing the flow in a fracture with irregular boundaries are solved with a nonstaggered grid distribution. Leakoff on the fracture surfaces is specified based on local permeability. This model uses front-fixing method1 (body-fitted coordinate transformation) to transform an irregular physical domain into a regular computational domain. A spatially correlated permeability distribution and initial fracture width distribution are generated by a semi-variogram model.
Results from the model illustrate the complex velocity field that occurs in fractures with heterogeneous distributions of fracture width and leakoff rate. The global flow rate versus pressure drop behavior from this model is compared with the predictions of smooth-walled fracture models.
Innovative Methods to Improve Carbonates Reservoirs Modeling Accuracy and Reliability
Authors: David Foulon , Den Boer Louise , Vieban Florence , Noman Rashed , Labiadh Mohamed 
Published: December 2007

Abstract
While they already contain around half of the world's hydrocarbon reserves, carbonate fields still exhibit lower recovery factors than clastic fields. A major explanation lies in the more complex intrinsic structure and higher chemical reactivity of carbonate rocks. Because it is linked to both the depositional and the biological environment, the genetic pore network is more complicated than in classical sandstones. Moreover; it is usually strongly reworked after deposition by superimposed diagenetic processes as well as fracturing phases. This creates levels of heterogeneity orders of magnitude higher than in clastic environments. As a result, small scale heterogeneity is often a key driver of fluid flow in carbonates. Proper, reliable modeling of this critical heterogeneity remains a pitfall often preventing efficient reservoir simulation and development.
This paper recaps the traditional upscaling methods used for heterogeneity modeling, and highlights their limitations when applied to carbonates. It presents an innovative line of thinking to overcome these limitations, grounded on robust geological concepts and tied to core and log data. The corresponding reservoir modeling involves the dual porosity structure, not for fracture modeling, but for splitting the porous medium between the fluid portion mainly involved in pressure support and the one sweepable liable to be readily swept.
This innovative workflow, coupled to smart experimental designs matching techniques, was applied to a mature carbonate field in the Middle East. It enabled to reach a first-time successful history matching, and to highlight significant additional development potential. Conceptually simple and numerically efficient, this methodology could be extended to other highly heterogeneous fields.
Underbalanced Drilling Of a Horizontal Well in Depleted Reservoir: A Wellbore Stability Perspective
Authors: Qiu Kaibin , Gerryo Yousef , Tan Chee Phuat , Marsden James Robert 
Published: December 2007

Abstract
The need to reduce formation damage and to avoid differential sticking and lost circulation in depleted reservoirs favors the use of underbalanced drilling (UBD) technology. In highly depleted reservoirs, the pore pressure can be very low, necessitating the use of extremely low-density fluid to achieve an equivalent circulating density (ECD) below the pore pressure. In such situations, the stress redistribution around the wellbore has to be supported mainly by the rock matrix, and limited support is provided by the mud pressure. Therefore, UBD can dramatically increase the risk of wellbore instability.
From literature review, it was found that the techniques and methodologies to carry out wellbore stability analysis on UBD of horizontal wells are not well documented. This paper presents a wellbore stability study that was conducted to evaluate the feasibility of using UBD technology to drill a horizontal well in a highly depleted reservoir in Libya.
The study started with geomechanical laboratory tests and Mechanical Earth Model (MEM) construction to evaluate the in-situ stresses, pore pressure, and mechanical properties of the formations likely to be encountered during the planned UBD campaign.
Wellbore stability analysis was subsequently conducted for the planned horizontal well to be drilled underbalance using a new practical approach. The analysis revealed a high probability of extensive and severe breakout within the weak zones if penetrated underbalanced and the potential for massive wellbore collapse. Under the guidance of this study, the well plan and drilling designs were amended to minimize drilling risk.
Smart Cementing Solutions for Low BHCT Wells—Case Studies for Successful Field Implementation
Authors: Banerjee Satinath , Dasgupta Debasish , Suyan K. M. , Jain V. K. 
Published: December 2007

Abstract
Cement slurry designing using conventional cement additives for primary casing cementation of wells with low / moderately low BHCT (40 – 70 Deg. C) generally encountered in shallow wells or in wells located in mature / depleted reservoirs is an industry challenge. Cement slurries for field implementation needs to possess adequate placement time, minimum fluid loss, good rheological behaviour, minimum free water separation, short transition time, good stability and early strength development capability under operational conditions. However, even with all the recent advancements in cementing technology, till today simultaneously meeting all of above requirements is extremely difficult for slurries designed with conventional cement additives.
In many onshore mature fields in India where ONGC is carrying out development drilling for the past several years, low / moderate BHCT wells are encountered. Due to technical limitations, job execution with inadequately designed cement slurry using conventional additives have resulted in many a case of poor casing cementation. As a result it was required to perform remedial cementation to overcome the undesired situation.
Extensive investigations have been carried out at Institute of Drilling Technology (IDT) in ONGC to formulate suitable cement slurry systems for low BHCT wells where all cement slurry parameters could be controlled simultaneously. This paper presents details of slurry designing with conventional additives by the incorporation of low cost silica based pozzolonic material. Studies have culminated in the development of novel slurry systems with unique feature that is was possible to have simultaneous total control over all crucial slurry parameters which could not be done earlier. The performance of developed designs have been elucidated and validated by field implementation in an onshore field of ONGC.
In the lesser explored area of slurry designing for wells with low BHCT, this paper established a low cost high performance alternative by the use of silica based pozzolonic material.
Field implementation results arising from this study confirmed superior cement bond logs in comparison to earlier results with no requirement of repair jobs. The details of the development, case studies of successful field implementation along with conclusions and recommendations derived from this endeavor are presented in this paper.
In-Situ Combustion Technique to Enhance Heavy-Oil Recovery at Mehsana, ONGC - A Success Story
Authors: Doraiah A. , Ray Sibaprasad , Gupta Pankaj 
Published: December 2007

Abstract
The northern part of the Cambay Basin located in Mehsana, Gujarat (India), is fenced by a number of heavy oil fields reserving about 140 MMT OOIP. Balol and Santhal fields form a part of this heavy oil belt with API gravity 15-18. The oil viscosity ranging from 50 to 450 cps at reservoir pressure of 100 kg/cm2 and 700C temperature. High mobility contrast between viscous oil and water has resulted into low primary recovery. Subsequent Artificial lift methods resulted into high water production rather than oil. Thus, it necessitated for in-situ combustion technique.
In-situ combustion is a thermal enhanced oil recovery process. The technique is based on the principle of reducing viscosity by heating of oil in the reservoir itself. It involves ignition in the well and injection of air to sustain flame front. In this process a small quantity of in-place oil burns, producing CO2, water vapours and heat. It helps in lowering the viscosity of oil, which increases the oil mobility and displace it towards the surrounding producers.
It is a matter of pride that ONGC, Mehsana has successfully implemented this technology. The project was initiated at Balol field on pilot scale in 1991. Based on encouraging results, in-situ combustion technique was implemented on commercial scale in 1997 at Balol and Santhal fields. It has not only given a new lease of life to these fields but has also increased the oil recovery factor from 6-12% to 39-45%.
Production engineering for in situ combustion involves careful planning and monitoring for successful implementation. Based on field experience, some of the major issues which came up during implementation are summarized in this paper. It can be helpful for successful planning and implementation of new projects
A Practical Approach For Preventing Lost Circulation While Drilling
Authors: Suyan K. M. , Banerjee S. , Dasgupta D. 
Published: December 2007

Abstract
Lost circulation problems encountered during drilling is caused by the differential pressure of the hydrostatic column which is generally greater than the formation pressure, and is especially through the openings in the rock in low pressure or depleted zones. Combating circulation loss is often achieved by using variety of LCM formulations or placing the cementing plug. The quick set sealing cementitious composition is formulated that produces cuttings compatible to drilling fluid. An engineering approach applied with the cementitious compositions admixed with synthetic fiberous LCM placed at the thief zone in the well set into a cementitious plug. The fiber based slurry allows setting in high permeable or fracture zone and caused strong impermeable net to prevent the losses.
Results from a laboratory study on cementitious formulations are discussed and compared with Portland cement plugs. The cementitious formulation designed with GGBS and silica fume admixed with synthetic LCM formed a slurry which is activated with calcium hydroxide. The sealing effect of the formulation has been evaluated against the sieves and slots of different sizes. The results revealed the substantial improvement in sealing the thief zone. The study of thickening time and compressive strength of formulations having sp gr 1.4–1.6 has been carried out at 60 deg C to get sufficient pumping time and strength to resume drilling within 3-4hrs. The contamination of drilling fluid with cementitious compositions has no significant changes in rheology that saves the extra expenses for conditioning the drilling fluid.
The paper presents various formulations of cementitious compositions which can be used effectively and economically to combat circulation loss during drilling.