bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unlocking the Low Frequencies for Improved Relative Impedance Inversion
Authors: Martin Iain , Helmore Steve 
Published: July 2010

Abstract
Seismic inversion techniques aim to estimate impedance and hence the Earth’s rock properties. Due to the band-limited nature of seismic data, estimates of absolute impedance require a low frequency scalar model estimated from horizon interpretation, well data and stacking velocities. Whatever deterministic inversion algorithm is employed, model assumptions and artefacts are embedded in an absolute impedance result.
Relative impedance inversion workflows avoid the pitfalls of a low frequency model by employing the seismic data alone, and are a fast and cost effective alternative when absolute impedance is not required. A typical workflow can be summarised by: Zero phasing of the seismic data by well ties or statistical methods; Relative impedance (‘Coloured’) inversion by spectral shaping and 90 degree phase rotation; Horizon based amplitude extraction and calibration.
The spectral shaping process applies a filter to the seismic reflectivity data to match it to the local well impedance spectrum. By wedge modelling we show that the range of bed thicknesses consistently imaged by the relative impedance is affected by the impedance wavelet characteristics, particularly the characteristic decay (α) of the spectrum with frequency, the low frequency cut-off, and the high frequency cut-off.
The decay (α) is determined by the local fractal layering of the earth and hence the log impedance spectrum. The degree to which the high and low frequency events can be imaged by seismic is limited by noise, and we can extract maximum value from the relative impedance result when the inherent impedance wavelet has high bandwidth.
Impedance data is particularly rich in low frequencies as a natural consequence of the Earth’s layering, and it is this low frequency bandwidth that new post-processing techniques aim to improve. Simple relative impedance inversions suffer from the amplification of low frequency noise if the shaping operators are pushed to their limits, creating a characteristic ‘curtain’ effect. We show how two recent processing techniques have solved this problem, extending the low frequency bandwidth often to as low as the acquisition low frequency cut-off.
The first innovation is to design and apply the inversion operator before migration, which reduces the problem to a 1D convolution and reduces low frequency noise. We demonstrate the improved performance of Coloured Inversion using this technique and the added value to a data set from West Africa.
The second innovation involves the application of structurally oriented filters to selected (low) frequency bands to improve signal to noise conditions prior to applying the inversion operator. We illustrate this technique with an example of relative impedance elastic inversion from the UK North Sea.
Using these pre-processing techniques on seismic data it is possible to produce products with high bandwidth and correctly estimate relative impedance over a large range of bed thicknesses, delivering valuable insights to the interpreter.
Evaluation of Triazine-Based H2S Scavengers for Stimulation Treatments
Authors: Al-Duailej Yaser K. , Al-Mutairi Saleh H. , Al-Humaidan Adel Y. 
Published: July 2010

Abstract
Acidizing fluids perform their functions through complicated processes, hence, require additional additives to achieve wanted goals and prevent harmful side effects. Examples of these additives are diverting agents, corrosion inhibitors, surfactants, de-emulsifiers, and iron control agents. These additives should be designed to perform in a compatible and synergetic way with other additives. In this paper, triazine-based hydrogen sulfide scavenger was investigated for its scavenging capacity in various fluid formulations and its compatibility with several additives.
To determine the scavenging capacity of the scavenger, an experimental method was developed. In this method, hydrogen sulfide (H2S) was generated by reacting hydrochloric acid (HCl) with iron sulfide (FeS), passed through a solution containing a triazine-based scavenger, and trapped in cadmium sulfate (CdSO3) solution. Then, the scavenging capacity was measured using gravimetric method. Furthermore, several testing parameters were investigated including amount of generated H2S, flow rate, concentration of scavenger, and type of solvent. All experiments were carried out in and aquatic neutral and acidic solutions at an anaerobic atmosphere and ambient conditions.
The second part of investigation was the compatibility of hydrogen sulfide scavenger with common acidizing additives. The objective was to determine the damaging or hindering effect caused by these additives. Tested additives were mutual solvents and quaternary ammonium corrosion inhibitors.
Water was found to be a suitable solvent for the tested scavenger. In contrast, the scavenging capacity declined dramatically when HCl was used. Therefore, optimum scavenging capacity, using water as solvent, was determined based on extensive testing that included parameters such as concentration of scavenger, amount of H2S, and contact time. Also, the tested additives were found to reduce the scavenging capacity.
A Novel Fracture Characterization Approach: Mini-DST Using a Wireline Formation Tester
Authors: Widjaja Danang R. , Alhuthali Ahmed , Guerrero Rodolfo Phillips , Lyngra Stig , Rourke Marvin 
Published: July 2010

Abstract
A good understanding of the fracture characteristics is essential for a successful development of a tight, heavily fractured reservoir. The fractures play a major role for both reservoir fluid flow and well productivity. An efficient fracture characterization is required to understand the recovery mechanism, which is critical for field development and optimal production strategy decisions. It is imperative that state-of-the-art dual-porosity/dual-permeability models are populated with accurate fracture descriptions to provide reliable forecasts.
This paper describes a novel approach to characterize fracture properties by using image logs, formation tester with straddle packers, and pressure transient analysis (PTA). The image logs are used to identify fracture systems along the wellbore. The formation tester with a straddle packer is used to isolate each system shown on the image logs for separate pressure drawdown and buildup testing. The fluid type filling the fractures can be identified during drawdown. The acquired pressure responses are interpreted by PTA to calculate the fracture properties and to determine the fracture role in the recovery efficiency.
Several essential results have been obtained. Range of matrix anisotropy, kv/kh, has been concluded. Role of small scale fractures on recovery mechanism has also been better understood.
Improving Seismic Whitening and Seismic Inversion Workflows Using Frequency Split Structurally Oriented Filters
Authors: Helmore Steven , Martin Iain 
Published: July 2010

Abstract
This paper describes a seismic processing method that uses dip-steered filtering to improve the performance of subsequent seismic whitening and relative impedance inversion. Given favourable acquisition and processing parameters, the availability of high frequency signals is ultimately limited by poor Signal/Noise ratio (S/N) at high frequencies. Managing this noise is key to accessing the high frequency information.
We show that although spatial filters applied to broadband seismic data mainly affect the central pass-band, a frequency splitting approach can specifically benefit targeted high frequency ranges in the spectrum. The dip steered filters trade spatial resolution for increased S/N, but only in targeted frequency bands that are boosted during the subsequent whitening process.
The S/N of the low frequencies can be improved using a similar process prior to acoustic impedance inversion. In a relative impedance inversion workflow, de-noising the low frequencies allows accurate inversion of thicker beds. Applying the technique prior to full-bandwidth inversion allows the use of lower seismic frequencies, and reduces reliance on a pre-existing background model.
We can apply frequency split dip-steered filtering to pre-stack common offset volumes or partial stacks in a similar fashion. This delivers frequency balanced partial stacks with lower noise and increased resolution, ultimately leading to a reduction of offset dependent tuning and higher resolution elastic inversion products.
Logs are not required for the process but independent well ties demonstrate the validity of the technique and are used to QC the products. The value of increased resolution in the seismic data volumes is illustrated with several case histories from different surveys and reservoirs.
Leveraging Slim Hole Logging Tools in the Economic Development of the Ghawar Fields
Authors: Ariwodo I. , Al-Belowi A. R. , BinNasser R. H. , Kuchinski R. S. , Zainaddin I. 
Published: July 2010

Abstract
Traditionally, brown field developments have often required the plug back and sidetrack of existing drain holes, to target any nearby opportunities. With advances in drilling technology, there is a general preference to drill small diameter wells due to the comparative cost advantage.
In the recent times, this preference has led some wireline service companies to start to offer open hole formation evaluation services with slim tools having a diameter in the 2" to 2½" range. At present, most of the traditional petrophysical measurements can be acquired utilizing slim tools. In addition, several "specialized" measurements, such as cross dipole sonic, formation pressure testing, and resistivity imaging can also be acquired. The use of battery and memory technologies has allowed these tools to be deployed using a broader range of conveyance techniques allowing for reduced risk in the entry of slim wells.
The provision of slim hole logging services has created an opportunity in the industry to leverage these tools for the economic development of brown fields. Therefore, short horizontal sidetracks and well re-entry’s to test deeper horizons can be drilled and logged successfully. Saudi Aramco has been able to leverage these tools in its continued development of the giant Ghawar field. Some of the development projects are listed below: Some horizontal sidetracks with 3⅞" hole sizes have been drilled under higher doglegs than was previously possible, and logged successfully.It is now possible to run well completions in newly drilled wells that have a well control problem. A provision is made to subsequently log these wells with slim wireline logging tools.It is now possible to run a complete suite of wireline logs across some old wells that were previously completed without a full formation evaluation logging suite.Slim hole formation resistivity imaging services are now being provided, to aid in the identification of borehole breakout and fracture features that might affect the well’s productivity.Slim hole formation pressure testing has been acquired in slim wells to generate a pressure gradient, determine oil mobility, and define oil-water contacts.
Several case studies will be used in this paper to demonstrate how Saudi Aramco has leveraged these slim wireline tools to realize some development opportunities. Also, examples will be used to show that these slim tools do not compromise the quality of log data acquisition.
A Novel Command Activated Sandface Valve To Improve Wellbore Productivity
Authors: Adam Malcolm , Coull David 
Published: July 2010

Abstract
A novel command activated sandface valve was developed that has significantly improved productivity by enabling improved wellbore clean up, particularly in high angle and open hole completions. The sandface valve technology has now seen 35 valves installed with a functional 100% success rate. Further wells are planned for a North Sea field utilizing this technology. The command activated sandface valve development was taken from concept to installation in 5 months including operator engineering reviews.
Inefficient wellbore clean up of highly deviated completions is common in production wells. Current solutions include Smart well technology or time consuming clean up procedures that are both expensive and difficult to implement. Poor clean up can lead to loss in well productivity, restricted access to reserves and in some cases a requirement to sidetrack the well.
An operator in the UK had observed no flow from the toe of the well while experiencing high drawdown at the heel section due to the dominance of high productive intervals.
The command activated sand face valve was developed from an operator’s requirement for more time control when selectively cleaning up/flowing the reservoir sections. The key objectives of the valve were to allow sequential clean up of the reservoir section from the toe to the heel without intervention or incremental rig time. The valve would be activated by a pressure recognition signal and also had to deliver the functionality of a sliding side door for future water shut-off capability along the well bore. The paper will present an overview of the technical challenges, detail development of the tool and processes used for assurance, and include results of the field trials.
The valve design combines a field proven timer activation mechanism, a transducer and conventional sliding sleeve technology. The tool was developed without external resource and cost often required for product development. Development of the valve was closely monitored by the operator which included a technical assurance review and failure mode and effects analysis process. The result is a successfully field proven completion tool that is the basis for a new completion technique that has application in high angle wells in all oilfield applications.
Value of 3D Geomechanical Modeling in Field Development - A New Approach Using Geostatistics
Authors: Holland M. , Brudy M. , van Der Zee W. , Perumalla S. , Finkbeiner T. 
Published: July 2010

Abstract
In recent years, the petroleum industry achieved marked advances in the development of full 3D and 4D geomechanical models. If robust, these 3D/4D models provide the benefit for more accurate well and field development planning in structurally complex settings such as areas with significant topography or/and faulting, when substantial depletion is likely to cause changes in the in situ stress field accompanied by reservoir compaction and even surface subsidence, or due to the presence of salt diapirs or other frictionless bodies/layers with different material characteristics. In most cases, these 3D/4D geomechanical models also require advanced finite element modeling coupled with reservoir simulation. In these instances, in particular understanding the in situ stresses, pore pressure, and material properties and their variability (lateral, in depth as well as with time) is of critical importance to better evaluate and mitigate risk during the drilling, completion, and production phase of a field development.
However, not all fields require the finite-element approach. In this paper, we demonstrate how a 3D geomechanical model can be build in a structurally relatively straightforward setting based primarily on an existing structural model and augmented with well data under application of appropriate geostatistics techniques to map and interpolate rock properties (such as density, rock strength, internal friction, etc) along the structural grid directly linked to the field's stratigraphy. This type of 3D geomechanical model has a clear advantage over a 1D depth-stretched model by honoring structural and stratigraphic constraints. This is particular important when an operator plans to drill a high number of directional or even horizontal wells and needs to capture varying stresses, pore pressures, and rock properties on the field scale to optimize well integrity. At the same time, this geomechanical model also provides benefits over 3D numerical modes in terms of timing to build the model, cost, flexibility to update the model (with data from additional offset wells) and accessibility across disciplines in the asset team. For example, it is straightforward to export data along planned trajectories for conventional wellbore stability analyses.
Effect of Temperature and Pressure on Interfacial Tension and Contact Angle of Khuff Gas Reservoir, Saudi Arabia
Authors: Okasha Taha M. , Al-Shiwaish Abdul-Jalil A. 
Published: July 2010

Abstract
Knowledge of reservoir fluid properties is essential during the development phase, and to implement an optimal reservoir management strategy for properly exploitation of tire reservoirs. Interfacial tensions (IFTs) of reservoir fluids, as well as the contact angle are important parameters for many reservoir engineering studies. Examples are imbibition studies and calculation of fluid saturation in the gas-oil transition zone.
Both IFT and the contact angle of the fluids/rock system affect the distribution of fluids within reservoir rock material. The fluids distribution strongly affects the flow behavior and hydrocarbon recovery. Most of the available data, contact angle and IFT for crude gas/brine systems are for room temperature and atmospheric pressure. Since actual values of reservoir temperature and pressure are frequently encountered in oil field simulation models, a need to study IFT and the contact angle at reservoir conditions was recognized. This paper is an investigation of the influence of temperature and pressure on IFT and the contact angle of Khuff gas and condensate fluids.
Experimental results of IFT for Khuff-C gas/brine system and condensate A, B and C/brine system over a range of temperatures and pressures are reported. Also, results of the contact angle for various samples of condensate/brine/rock material systems are documented. The IFT between Khuff-C gas and brine decreased with increasing temperature at the maximum system pressure of 3,000 psi. Condensate composition effects on IFT were seen for various condensate samples (Khuff-A, B and C ). The contact angle values for Khuff-C gas/brine/rock material system decreased with both temperature and pressure.
Determination of Reservoir Rock Wettability by Thin Layer Wicking Approach
Authors: Yildiz Hasan O. , Oztorun F. Bahar , Sirkeci Ayhan A. 
Published: July 2010

Abstract
The present study was an attempt to investigate the possibility of contact angle determination of two immiscible fluids in contact with the solid surface of a porous material with heterogeneous mineralogical composition. Since the contact angles are measured on a single mineral’s crystal, the question of how representative the results of wettability of the rock containing many different constituents arise. Due to the roughness, heterogeneity, and absorption ability of porous surfaces of reservoir core, the direct measurement of contact angle is not applicable. When contact angles cannot be directly measured, the measurement of capillary rise in a bed of particles can be used to quantify wetting characteristics of the solid. The main objective of this study was to investigate the determination of rock wettability by Thin Layer Wicking approach. The application of the Washburn equation for dynamic measurement of contact angle and the method of Thin Layer Wicking were described. Experiments were conducted on the powdered samples of different sandstone and limestone rock samples and also their representative pure minerals such as quartz and calcite, respectively. As a wicking test liquid, distilled water, 2% NaCl brine, kerosene, and mineral oil were used, and their contact angles with respect to the sample’s solid surface were calculated. Powdered sample of quartz mineral was proved to be more water-wet than powdered sample of calcite mineral. Furthermore; the contact angle values of carbonates are closer to that of calcite while the contact angle values of Berea and Bentheim sandstone are closer to that of quartz. This study is the first Thin Layer Wicking study in Petroleum and Natural Gas Engineering Field, and it can be a leading survey to attempt new investigations in this subject.
Effect of Borehole Inclination, Annular Clearance, on the Hole Cleaning Efficiency for Water Based Drilling Muds
Authors: Noui-Mehidi Mohamed N. , Amanullah Mohamed 
Published: July 2010

Abstract
In the case of deviated, horizontal, extended reach and multi-lateral wells, the existence of a particle bed and also the formation of a partially or completely buried cuttings bed can be problematic for borehole cleaning. As a solution increasing the drilling fluid velocity can help in eroding the deposited bed substantially above a critical velocity, which depends on several flow parameters. For instance pipe rotational speed can enhance particle transportation at flow velocities lower than the critical annular fluid velocities as reported in the literature. The consequences of pipe rotation on the fluid transport ability are also subject to the inclination of the drilled section. The present paper discusses the results of numerical simulations of water based drilling fluid flows regarding the inclination effect, the fluid viscosity, the clearance between the pipe and the borehole and the resulting pressure losses.
Azimuthal AVO in Coal Beds, Western Canadian Basin: A Promising Method for Characterizing Fractures in Unconventional Gas Reservoirs
Authors: Al-Duhailan Mohammed A. , Lawton Don C. 
Published: July 2010

Abstract
Seismic analysis was conducted to predict the orientation of the dominant fracture (cleat) system in a Cretaceous coal bed gas reservoir within the unconventional Coal Bed Methane (CBM) play in central Alberta, Canada. The extension of the method of analyzing the variation of seismic amplitude as a function of offset (AVO) to include analysis of amplitude variation as a function of azimuth (azimuthal AVO) was utilized. This technique was applied to characterize seismic azimuthal anisotropy, which indirectly predicts fracture system orientations.
The study focuses on identifying the azimuthal variation of the AVO response of the coal bed. By calculating three azimuthal AVO gradients from 2D multi-azimuth walkaway vertical seismic profiles (VSPs), the study revealed the existence of azimuthal anisotropy. A mathematical solution using these calculated AVO gradients defines the direction of the maximum change in amplitude with offset. This direction is always perpendicular to the orientation of the dominant fracture system.
The reliability of the approach used in this study demonstrates a promising method for characterizing fractures in unconventional gas reservoirs.
Production Optimization of Multi-Lateral Wells Using Passive Inflow Control Devices
Authors: Hembling Drew , Berberian Garo , Al-Mumen Adib , Simonian Sam , Salerno Giovanni 
Published: July 2010

Abstract
Passive ICDs (Inflow Control Devices) are being used to enhance performance of horizontal wells in unfavorable enviromnents such as non-uniform permeability and/or pressure variations along horizontal sections. This is the first ever attempt, to the best of our knowledge, at using ICDs to manage inflow from two laterals connected to a motherbore. Furthermore, this well is a 3 7/8" openhole multi-lateral with a 2 7/8" ICD completion.
This paper presents how passive ICD completion technology is used to optimize well productivity in a multi-lateral well. This carbonate well was sidetracked to increase reservoir contact and create tire required multi-lateral. Subsequently, the ICDs were run, and to confirm the inflow profile along the length of the of the ICD completion, a PLT survey was conducted. The actual rate and inflow profile compared favorably with the predictions as per design of the ICD completion. This paper will show the well design, the actual PLT vs modeled results, and discuses future utilizations for this technology.
The key factor in the success of this project was the use of the 2-7/8" ultra-slim ICD completion, which was optimized based on numerous wellbore hydraulic simulations, to determine the appropriate number of ICD units and compartments to balance the required off-take from each lateral, and from individual compartments in the motherbore section.