bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unconventional Multiple Fracture Treatments Using Dynamic Diversion and Downhole Mixing
Authors: Surjaatmadja Jim B. , McDaniel B. W. , Sutherland Rod L. 
Published: December 2007

Abstract
This paper reviews a unique, relatively new stimulation process that uses dynamic fluid energy (instead of mechanical methods) to isolate treatment fluid flow to a specific fracture point along the wellbore. A process of hydrajet-fracturing has been developed by merging four existing technologies: hydrajetting, hydraulic fracturing, jet pump technology, and dual-path fluid injection. These have been meshed to create a method whereby a wellbore is perforated (if necessary) and a fracture is initiated and placed accurately at a specific location, and then soon repeated at another chosen location uphole, or closer to the heel when in a lateral wellbore. The process was later expanded as a hydrojet-squeeze stimulation method also, even to the point of applying both of these applications while stimulating a single wellbore.
This process employs two independent fluid streams: one in the treating string and another in the annulus. As these fluid paths will be supplied with separate pumping equipment, we have the option to instantaneously alter the downhole mixture that is being used to treat the formation at the current location of the jetting tool. An additional use of this two-stream feature is the capability to pump two different fluids that can be mixed downhole with a tremendously high energy to form a homogenous mixture at the fracture entry point, even creating foamed fluids insitu for some applications.
This technique has been used to stimulate more than 50 horizontal or highly deviated wells (and a few vertical wells) as of the preparation of this paper, both proppant-laden fractures and fracture acidizing treatments. On average, more than 7 fractures were placed along a typical horizontal wellbore, typically several hundred feet apart without the use of mechanical sealing equipment. Additionally, numerous horizontal wells with higher permeabilities have been stimulated using the hydrajet-squeeze process alone.
The diversion process follows a dynamic isolation approach that uses a high-velocity, high-energy jetted fluid. The process was originally developed for its unique stimulation capabilities in openhole horizontal wells, but has been extended to wells that have cemented or non-cemented liners, whether vertical, deviated, or horizontal and even to multilateral completions (or recompletions).
This paper offers insight into many of these treatments, including the different well situations, design considerations, operations, and available results of the treatments. Possible unconventional approaches using this concept and a unique implementation in the field are also discussed.
Fiscal Regimes Competitiveness Comparison of Oil and Gas Producing Countries in the Asia Pacific Region: Australia, China, India, Indonesia and Malaysia
Authors: Dharmadji Temmy , Parlindungan Tumbur 
Published: December 2007

Abstract
Fiscal Regimes is one of the most important factors to be considered for investment decisions in oil and gas industry. Royalty Rate, Cost Recovery, Contractor Share, Domestic Market Obligation, Investment Credit, Signature Bonus, Production Bonus, First Trance Petroleum and Corporate Tax Rate have a significant effect on the investment decisions.
The paper examines and compares the fiscal regimes in Australia, China, India, Indonesia and Malaysia. In order to analyze the advantages and disadvantages of each fiscal regime, the economic analysis of the same hypothetical fields with the applications of those different fiscal regimes are presented and discussed. Generic fiscal terms are used in the analysis since contractors usually can negotiate the special terms with governments.
The information of this paper is useful for oil and gas companies around the world when they want to decide where in Asia Pacific Region they want to invest their money. They can compare which fiscal regime gives them the most favorable return of their investment. In addition, the information is useful for the governments when they want to assess their fiscal regime competitiveness compared to other fiscal regime in that region. In depth analysis on fiscal regimes of those countries is very important for oil and gas industry and it will add to the knowledge base of this industry.
Conclusions are made of the effects of these different fiscal regimes on oil and gas company cash flow and profitability and how they affect company investment decisions in oil and gas industry and government policy.
Relative Permeability Measurements of Composite Cores, an Experimental Approach
Authors: Zekri Abdulrazag Y. , Almehaideb Reyadh A. 
Published: December 2007

Abstract
Some experimental tests require floods to be carried out on longer cores, typically 1–3 feet long. When whole cores are not available, side-wall cores each measuring 3–6 inches long are put together to make a composite core. It is the prevailing practice in the industry for composite core floods to order cores in an ascending permeability order, as this is thought to lower capillary forces for high flow rates and thus lessen the capillary end-effect. Huppler (1969), through a numerical study and neglecting capillary end-effects, proposed the criteria that cores should be ordered in such a way that the harmonic average between sections should be as close as possible to the overall average of the composite. Also, the core with permeability closest to the average is placed at the outlet position. Recently, with certain assumptions, Langaas et al. (1998) have demonstrated through a theoretical study that a new criteria should be followed, i.e. ordering cores in a descending order. They showed that this would produce residual oil saturation closest to the value for the composite, if it were considered as a single core with average properties. In this work, we present results of an experimental composite core flooding study that was designed to test how the properties of the individual cores in a composite core-stack influence the measured residual oil saturation and relative permeabilities for an oil-water system typical of a water flood. The study was conducted for carbonate cores, predominant in the lower Arabian Gulf region, and involved composite cores stacked in an ascending, descending, and random order (according to the Huppler criteria). Results of the experimental runs in this study show a significant effect of ordering on relative permeability evaluation, with values for Krw and Kro for composite cores in a descending order significantly different from the values for both random ordering and ascending ordering. Also, the recovery factor was highest for the composite core ordered in a descending order, followed by ordering according to Huppler's criteria, and then ascending order. These findings support Langaas et al. findings, i. e. the best ordering criteria is after decreasing permeability along the flow direction such that the core with the highest permeability is placed at the inlet.
Sample Quality Prediction with Integrated Oil and Water-based Mud Invasion Modeling.
Authors: Proett Mark A. , Chin Wilson , Wu Jianghui , Manohar Mohan , Belanger Dave 
Published: December 2007

Abstract
Wireline formation sample contamination and quality control depend on formation parameters and mud characteristics. The invasion process is a complex multi-phase problem particularly when mixed miscible and immiscible fluids are present. The scenario is complex when either oil-based mud (OBM) or water-based mud (WBM) invades a reservoir with initial oil-water concentration. Either oil or water may be the principal contaminating fluid depending on mud type. This paper presents the results of analyses based on the first wellbore invasion simulator that models the complete problem. The governing differential equations for miscible and immiscible fluids, with fluid compressibility, rock heterogeneity and anisotropy, and gravity are developed from first principles and implemented in a finite difference code. In addition, general boundary conditions allow dynamically coupled mudcake growth, which do not assume that mudcake completely controls invasion into the formation. The simulator developed also allows bed boundary modeling as well as assessment of multi-probed pumping.
Previous invasion simulations in the literature are based on two-phase immiscible fluids where WBM invades an oil zone. Of greatest interest, however, in sampling quality is the OBM invasion problem. OBM contains a mixture of oil and water, where the oil is the continuous phase and encapsulates the water. The continuous mud filtrate phase dominates the invasion and, according to molecular diffusion dynamics, mixes miscibly with formation fluids. The effects of anisotropy, mudcake growth, gravity, and two-phase flow properties on this problem can thus be assessed.
While invasion has a strong influence on potential sample quality, the pumpout wireline formation tester (PWFT) sampling procedures can be designed to have an equal influence on sample quality. The new simulator can evaluate the concentration of the fluid phases and types during the sampling process.
Although it is a fact that sampling rate as well as the placement of a probe within a zone can have an impact on sample quality, in practice the oil's bubble point pressure limits the sampling pumpout rate. However, if a tester is equipped with more than one probe, as the new tester is, pumping through both probes can increase sampling rates. Additionally, if the sampling probe is placed near a permeability barrier, a further improvement on sample quality can be expected. All of these options can potentially improve sample quality and reduce pumpout time.
To study these effects a sensitivity analysis has been performed using the simulator to determine the impact sampling procedures have on sample quality. PWFT log examples are used to compare with the simulated results.
Planning A Successful Accident Preventional Program
Authors: Homewood C. 
Published: December 2007

HOMEWOOD, C., ARABIAN AMERICAN OIL COMPANY

Introduction
Accidents have plagued man since the beginning of time. They have caused him injury. They have caused him property damage and loss. And sometimes they have cost him life. Accidents often have been considered inevitable. In one sense, they are—they are the inevitable result of human failure.
Accidents have changed the course of history. They certainly change the course of our life if we are the injured or our property is lost or damaged. Accidents have increased to such a degree in modern life that they require our best efforts to prevent them. Much is available in the literature of the world on how to prevent accidents, and I am sure this paper will give nothing new in accident prevention. But if it re-emphasizes safety fundamentals, it will serve a useful purpose.
There has been some tendency to limit accident prevention to study of injury-producing ones and to overlook accidents that cause damage or loss of property. This tendency is understandable. Personal injuries are rightly more demanding of our attention than destruction of property. But this limited view has delayed progress in accident prevention.
I think it is appropriate to define the word "accident" as a professional safety engineer uses it:
"An accident is any unexpected event that interrupts of interferes with the orderly of production, activity, or process."
Under this definition, an accident may cause damage to equipment or material or cause a production delay without resulting in an injury. It is here that the campaign to prevent accidents must start for almost every accident has the potential of causing injury.
Effect of Pore Pressure and Stress Path on Rock Mechanical Properties for HPHT Application
Authors: Skomedal E. , Jostad H. P. , Hettema M. H. 
Published: December 2007

Abstract
A laboratory testing program was performed to investigate the behavior of the sandstone of an HPHT reservoir when subjected to realistic in-situ stresses, pore pressures and stress changes due to production. Volumetric changes, stress path effects, plastic deformation and strength were included. It was found that the Terzaghi effective stress definition was most suitable to handle the different mechanisms. Relevant material properties were defined, and a basis for geomechanical engineering of drilling and production of the HPHT reservoir was established.
Mud Chemistry Effects on Time-Delayed Borehole Stability Problems in Shales
Authors: Fjær Erling , Holt Rune M. , Nes Olav-Magnar , Sønstebø Eyvind F. 
Published: December 2007

Abstract
A combination of small sample testing and numerical modelling offers a powerful tool for identification of mud chemistry effects on wellbore stability in shales. The tool allows for modelling of how the stability limits for the mud-weight varies with time, based on measured time scales and magnitudes for the various processes involved. It may also assist in estimation of the optimal amounts of chemical additives in the mud.
Predicting Volumetric Sand Production in Weak Reservoirs
Authors: Chin L. Y. , Ramos G. G. 
Published: December 2007

Abstract
In general, sand production in oil/gas reservoirs in weak formations has an adverse impact on production costs. For efficient reservoir management, predictive tools are needed to quantitatively mitigate and control sand production. A fully coupled sand production model that integrates geomechanics and fluid flow was developed to quantify volumetric sand production during the early drawdown period (a few days), bean-up, as well as in the depletion period (a number of years).
First, we compared simulation results from the proposed model to sand production data from full-scale laboratory perforation sanding tests for model verification. Then, we employed the developed model to evaluate the key variables that govern volumetric sand production. This study indicates that sand production in weak reservoirs is influenced by a number of variables. These include rock strength, flow rate, oil viscosity, and producing time. The simulation results relating cumulative sand production and sand production rate to these important variables are presented. Descriptions of the volumetric sand production model (formulations, constitutive equations, solutions procedures) are also presented.
The study suggests that the proposed model may be used to generate quantitative information for predicting volumetric sand production. This provides a tool for sand-management in exploiting the weakness of sanding-prone scenarios.
Experimental Observation of Injection Rate Influence on the Hydraulic Fracturing Behavior of a Tight Gas Sandstone
Authors: Zeng Zhengwen , Roegiers Jean-Claude 
Published: December 2007

Abstract
It has been widely accepted in hydraulic fracturing that the higher the pressurization rate, the higher the breakdown pressure. However, linear elastic fracture mechanics (LEFM) suggests the opposite. In an effort to clarify this "injection rate paradox," three controlled laboratory hydraulic fracturing experiments were conducted using different injection rates. These tests showed that the higher the injection rate, the lower the breakdown pressure. Further investigations indicated that the elastic- and poroelastic- models were not able to properly predict the observed breakdown pressures. Using Griffith's energy balance concept, an LEFM-based breakdown pressure model was derived which gives satisfactory predictions.
Equilibrium Test - A Method for Closure Pressure Determination
Authors: Weng X. , Pandey Vibhas , Nolte K. G. 
Published: December 2007

Abstract
Minifracs are routinely pumped before fracturing treatments to determine the in-situ fracturing parameters such as fracture closure pressure and fluid leak-off coefficient. These parameters are essential for design adjustment, pressure match, and fracture dimension estimate. The method most commonly used for determining closure pressure is pressure decline analysis during the shut-in period, using G-function plot, square-root time plot or other plots. Unfortunately, the shut-in decline data is often difficult to analyze and can yield inconsistent and erroneous closure pressures.
A new injection test for closure pressure determination, called &quot;equilibrium test&quot;, is described in this paper. In the test, a fluid is first injected at a normal fracturing rate for a period of time to create a hydraulic fracture, and then pump rate is dropped to a small rate and held constant. The treating pressure will initially decline as in the conventional shut-in decline, but will gradually level out and start increasing, when equilibrium between the small injection rate and the leak-off from the fracture is reached. The pressure response can be easily analyzed to obtain an estimate of closure pressure. Fluid efficiency can also be estimated from the decline slope. A detailed discussion of the method, analytical calculations for determining the closure pressure and several field cases are presented in this paper.
Discrete Element Approach for the Wellbore Instability of Laminated and Fissured Rocks
Authors: Yamamoto K. , Shioya Y. , Uryu N. 
Published: December 2007

Abstract
A laminated and fissured formation around a horizontal borehole is modeled as a combination of intact rock blocks and permeable fractures with a DEM code. The model is used for understanding the mechanism of rock failure problems observed in a shale formation of an offshore field. Different mud weights and stress conditions are applied to the model to simulate the rock failure around deviated holes in laminated and fissured shale.
The numerical simulation shows that shear failure along the bedding planes is the predominant mode of collapse of the hole when mud under pressures penetrate into bedding planes on which shear stress is applied. The severity of wellbore instability varies with stress states and wall conditions. The effect of a plugging agent in mud is verified by comparison between permeable and impermeable wellbore models.
Estimation of Stress Profile with Depth from Analysis of Temperature and Fracture Orientation Logs in a 3.6 km Deep Well at Soultz, France
Authors: Ito T. , Fujii R. , Evans K. F. , Hayashi K. 
Published: December 2007

Abstract
We presented a new method for stress measurements which is based on the hypothesis that fractures which are critically-stressed for frictional sliding in the current stress field tend to permeable and those which are not critically-stressed tend to be impermeable. Fracture depth, dip and strike can be detected from borehole imaging logs such as BHTV/UBI or FMI/FMS. By comparing the depths of fractures and those of thermal anomalies detected on temperature logs, we can identify which of the fractures are permeable. Stresses on fracture planes can be estimated from the fracture orientation provided that the state of in-situ stress is assumed. Therefore, knowledge of which fracture orientations tend to be permeable and hence support critical stress states, and which fracture orientations are not allows us to make a grid search over possible states of stress to identify the stress state that best satisfies the observations and hypothesis. A simple description of the stress states is necessary. Assuming that one principal stress is vertical and equal to the overburden and pore pressure is known, the stress states are defined by three unknowns given by the two depth gradients of the two horizontal stresses, and the orientation of the maximum horizontal stress. The range of admissible stress states can be further reduced by considering the strength of the bulk rock. We applied the method to estimate stress state about a 3.6 km deep well in granite at the Soultz Hot Dry Rock test site. Fractures and thermal anomalies detected in the depth range of 2850∼3500 m were used for the estimation. Results indicate that the stress regime is one of normal/strike-slip faulting, consistent with the fault plane solutions of induced and regional earthquakes. The predicted profile of minimum principal stress magnitude agrees with that determined from the hydrofracture method. The inferred orientation of the maximum principal stress differs from the best available estimate (defined by thermally-induced tension fractures) by 20∼30°. The example demonstrates that the method can yield useful estimates of the state of stress at great depth from relatively common data of temperature, borehole imaging, and density logs without requiring any additional input from expensive test. The method can also be applied in high temperature environments where conventional approaches to stress estimation cannot be applied.
Challenges for Monitoring and Verification of Drill Cuttings Reinjection Performance
Authors: Abou-Sayed Ahmed S. , Guo Quanxin , Wang Gary , McLennan John D. , Zaki Karim 
Published: December 2007

AbstractTo a certain extent, the success of drill cuttings reinjection (DCRI) has been serendipitous. Aggressive operational parties initially implemented the technique with support from far-seeing researchers. With the favorable economics incentive along with successful and safe implementations, drill cuttings reinjection has been further refined over time with established methodologies for attempting to more precisely predict placement of large solid volumes. There is a need now for verification and accurate monitoring of the process.This paper reviews standard technologies for monitoring cuttings placement; including pressure-time evaluation during and following injection using conventional methodologies, pressure transient evaluation technologies during and between batches. These techniques include interference techniques where appropriate, microseismic monitoring, tiltmeter surveys and logging methods. Future challenges and developments of each relevant technology are suggested in more detail. For example, tiltmeter methodologies have been successfully used in many situations but there remain issues in certain environments, i.e., in some layered scenarios. A good example of this relates to the difficulties that might be encountered in inverting tiltmeter data in arctic regions where DCRI takes place below an extensive permafrost layer. Another example relates to refining concepts for predicting multiple fracture geometries. Most practitioners are familiar with the disposal domain concept where batch-injected fractures are attributed to a simplified and regular three-dimensional domain, with no specific indication of individual fracture morphology. To date, precise prediction of domain geometry from pressure signatures or surface tilts has been weak. Simple methods are presented for identifying from pressure records or surface profiles the three-dimensional extent and near-well azimuths of multiple fractures.
Real-Time 4D Passive Seismic Imaging of Hydraulic Fracturing
Authors: Maxwell S. C. , Urbancic T. I. , Demerling C. , Prince M. 
Published: December 2007

Abstract
Passive microseismic imaging of fracture growth during hydraulic fracturing provides detailed images of the fracture geometry, including fracture dimension, orientation and complexity. The technology can be applied in real-time, during the stimulation, to provide time-lapse, 4D seismic images of the fracture growth. Here we present a number of case studies that illustrate how these images can then be used to improve the implementation of intended stimulation designs. The case studies demonstrate the feasibility of assessing the effectiveness of flushing an unexpected screen-out, imaging proppant placement, and controlling fracture geometry.