bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three-Dimensional Analysis on Stress Patterns within a Sub-salt Formation and an Integrated Method for the Design of a Mud-Weight Window
Authors: Shen Xinpu 
Published: March 2015

Abstract
Borehole stability and pore pressure environments downhole transition abruptly, often detrimentally in the presence of salt formations. Geomechanical regimes can vary considerably above, through, and below salts, making accurate modeling of them necessary but challenging. This paper proposes an integrated method that has been developed for predicting the Mud-Weight Window (MWW) of subsalt wells. The high efficiency of the 1D method and high accuracy of the 3Dmethod are deliberately combined in the proposed integrated method, while the disadvantages of those methods are avoided. This objective is achieved by calculating the effective stress ratios, which are part of the input data of the 1D method, with a 3D finite-element (FE) model. The effective stress ratio brings a 3D property into the 1D solution of MWW, thus giving it a 3Dproperty.
A 3D model, where the wellbore trajectory was accurately referenced, was built to illustrate and validate the proposed method. A salt body with a thickness of 5.8 km was included. The distribution of the effective stress ratio within the model has been calculated and used in the numerical prediction of the 1D MWW. The prediction of a 3D MWW corresponding to the wellbore trajectory is then derived in the subsalt formation and merged with the numerical prediction.
An Experimental Study on Mitigation of Oil Well Cement Gas Permeability
Authors: Ozyurtkan M. Hakan , Altun Gursat , Mihcakan I. Metin , Serpen Umran 
Published: March 2015

Abstract
Permeability development within and around the cement, placed in the casing-hole annulus in oil and gas wells, is a frequently encountered worldwide problem that might lead to various adverse economic and, possibly, catastrophic consequences. The resultant loss of hydrocarbon production and, sometimes, the wells constitutes the major part of the adverse economic impact. The loss of wells, in turn, might lead to severe environmental pollution and most importantly the loss of lives. Sustained casing pressure (SCP,) described as the pressure buildup due to flow through the permeable cement matrix or the micro annulus developed around the cement, had been experienced by about sixty percent of the wells producing oil and/or gas in the Gulf of Mexico, according to the literature. Although various methods are used to prevent the problem, there is no widely accepted universal method by the industry. Currently, the problem is attempted to be mitigated using distinct methods applied either during the cementing operations or after the problem is detected.
The present study is an experimental investigation for the prevention of permeability development within and around the set cement at ambient conditions. A natural magnesium complex with carbonate, coded ARI, is used the first time ever as a cement additive to achieve desired prevention. Gas permeability measurements are conducted on the samples of cements of 19 different compositions, at the end of the successive curing periods up to 28 days. ARI containing cement samples are found to develope an impermeable matrix to gas flow and to exhibit no shrinkage in volume during setting. The performance of ARI as a cement additive is also investigated in the presence of other commonly used cement additives, e.g. friction reducer and fluid loss controlling agents.
Comparative Study on Stress-dependent Permeability of Ultra-low Permeability Sandstone Rock Using Different Types of Fluid Media
Authors: Qi Teng , Junchang Sun , Zhengming Yang 
Published: March 2015

Abstract
During the production lifecycle of a reservoir, rock permeability may change due to the increase of the effective stress which could significantly affect well productivity. The main objective of this paper was to investigate stress-dependent permeability of ultra-low permeability reservoir rocks using different types of fluid media. Meanwhile, wettability and its effect on stress-sensitivity permeability were also studied in this research.
A total of twenty-seven sandstone rock samples selected from Daqing oilfield reservoir rock and Changqing outcrop rock was used to conducted permeability stress-sensitivity experiments. The gas permeability of those rock samples ranges from 0.0029mD to 7.7603mD. Experimental results indicate that gas permeability, brine permeability and oil effective permeability at irreducible water saturation all decrease with the increase of the effective stress. Most of the reduction of gas permeability and oil effective permeability takes place over the range of 2 to 16MPa effective stress. Comparative results show that reduction of brine permeability is larger than that of gas permeability over the same range of effective stress when the rock gas permeability is greater than 1mD. However, decrease of gas permeability is larger than that of brine permeability when rock gas permeability is less than 1mD. The oil effective permeability is more stress-sensitivity than gas and brine permeability. Reduction of the oil effective permeability is much greater with the increase of the effective stress when the rock samples have been aged in crude oil.
This research suggested that it may lead significantly error when gas was used as the fluid media in evaluating permeability-dependent of ultra-low permeability reservoir rock and its effect on well productivity. In addition, reservoir wettability should be considered when oil was used as the fluid media in permeability stress-sensitivity evaluation experiment.
Study on Matching Relation Between Polymer Molecular Size and Pore Size for Conglomerate Reservoir
Authors: Wenli Luo , Desheng Ma , Xiaobin Nie , Meiqin Lin , Qingxia Lin , Jian Fan , Hang Long 
Published: March 2015

Abstract
The matching relation between the molecular size of polymers and the pore size of Karamay conglomerate reservoir in Xinjiang oil field was studied. By employing the nuclepore film filtration method, core flooding experiments and dynamic light scattering method (DLS), the molecular size of several candidate polymers for the pilot test was examined. And several suitable polymers for different reservoirs permeability were obtained. In the microporous membrane filtration experiments, the polymer DQ3500 with the molecular weight of 3.57 × 107 matched the 0.7 mm microporous membrane well. Moreover, three polymer samples including DQ2500 (molecular weight 2.42 × 107), complex polymer BCF (molecular weight 2.42 × 107) and complex polymer ABCF (molecular weight 2.14 × 107) matched the 0.6–0.7 mm microporous membrane well. No retained aggregation was observed on the microporous membranes for all examined polymer samples. Both resistance coefficient (Fr) and residual resistance coefficient (Frr) were measured with five core polymer flooding experiments. Polymer solution including DQ3500 and DQ2500 with the concentration of 1000 mg / L were injected into the artificial cement conglomerate cores with permeability of 121 × 10-3-1000 × 10-3 µm2. The values of Fr and Frr increased with the increasing of polymer molecular weight and decreased with the increasing of core permeability. The average polymer coil hydrodynamic radius (Rh) was measured by the DLS method. The Rh ranged from 266.0 nm to 394.5 nm for the polymers with molecular weight from 2.14 × 107 to 3.57 × 107. Accordingly, the conglomerate reservoir with water permeability more than 55.4 × 10-3 µm2 could not been blocked by those polymers with molecular weight less than 3.57 × 107.
Quantitative Estimation of Gas Saturation by Frequency Dependent Avo: Numerical, Physical Modelling and Field Studies
Authors: Li Xiang-Yang , Wu Xiaoyang , Chapman Mark 
Published: March 2015

Abstract
It is well known that seismic amplitudes contain important information which can be related to fluid saturation. Most interpretation is based on Gassmann's theory and studies of amplitude variations with offset (AVO) with the Zoeppritz equations. However, this traditional AVO technique is often unable to make quantitative estimation of the gas saturation, hence unable to distinguish between commercial and non-commercial gas deposits. Recent attention has focussed on if the frequency response of reflections can also be used to reveal fluid information through the application of frequency-dependent AVO (FAVO), although many of these studies are based on empirical relationships and are lack of a thorough understanding of the underline mechanism and rock physics principles.
In this study, we extend the "squirt-flow" model to include the effect of gas saturation on seismic attenuation and dispersion. Combining with Wood's formula, the FAVO response can be calculated as a function of porosity and gas saturation. Therefore a model-based inversion scheme can be established by matching the calculated FAVO response to the observed ones for quantitatively estimating the gas saturation. There are three technical contributions in this approach:a theoretical frame work for modelling the FAVO response and the effects of gas saturation on seismic attenuation and dispersion;an efficient spectral decomposition algorithm for extracting the FAVO response from real data;an optimization work flow for estimating the gas saturation.
In our examples, the numerical modelling is able to predict the FAVO response to changing gas saturation which is seen in the physical modelling data, and the 3D P-wave field seismic data. Consequently we argue that with a careful model-based approach, it is possible to invert the FAVO response in terms of gas saturation. This may have important implications in the exploration of tight and unconventional gas resources.
Scale Management in Mature Gas Field: Case Study of Peciko
Authors: Bajammal F.A. , Biyanni H.M. , Riksa A.P. , Poitrenaud H.M. , Mahardhini A. 
Published: March 2015

Abstract
Peciko is one of the giant gas fields located in the Mahakam area, Indonesia, operated by Total E&P Indonesie. Since start up in December 1999, until May 2012, the average wellhead pressure and temperature of its wells have decreased from 150 barg to 20 barg and from 95 °C to 60 °C, respectively, while the average water/gas ratio (WGR) has increased from approximately 2.5 to 20.5 bbl/MMscf. These dramatic shifts of production parameter and borehole environment are believed to be the main factor of the increasing rate of scale deposition in significant number of its wells in the last few years. The nature of the scale encountered is mainly calcium carbonate and iron carbonate.
Reviews have been carried to better understand the phenomena of scale formation in the field and to formulate the optimum solutions in overcoming it. Guidelines have been established to facilitate early detection or prediction of scaling, which includes routine water analysis, periodic check of tubing clearance, and running multifinger caliper in the well.
Numerous attempts of removing the scale have been tried, with mechanical and/or chemical techniques, from light intervention using slick line unit, until semi-heavy intervention with coiled tubing unit (CTU). Several successful results have been observed, to some extent. Calcium carbonate scale showed to be relatively easy to remove, but the presence of iron carbonate imposes more challenge and complication. The milling operation, in particular, has been improved to minimize the negative effect of liquid circulation in sensitive wells, i.e. evolving from CTU milling using brine, to CTU milling using nitrified base oil, to electric line milling without liquid circulation.
The guidelines, lessons learned, and the foreseen solutions are considered as the key elements of scale management in the field, and will be described further in the paper.
Evaluation of Inflow Control Devices to Reduce the Water Production in Horizontal Wells of the Orinoco Heavy Oil Belt
Authors: Vasquez I.Y. , Rodriguez J.R. , Fernandez E.A. 
Published: March 2015

Abstract
The Orinoco Heavy Oil Belt, located in the southern part of the Eastern Basin of Venezuela, is considered the largest deposit of heavy oil in the world. It covers an area of 14 million acres and is characterized by having crude of low API gravity (from 7 to 10º), high viscosity (from 1,000 to 10,000 cp), high porosities (from 18 to 40%) and permeabilities that can reach 30 darcies. Heterogeneity is present in the Faja, there some areas with active bottom aquifers. On these particular areas an early water breakthrough has been identified in some horizontal wells.
A numerical simulation model with representative properties of an area of the Orinoco Heavy Oil Belt was defined to assess if the implementation of inflow control devices (ICDs) could reduce water production in horizontal wells. The numerical model contained a horizontal well where these completions elements were installed. The evaluation was made through a sensitivity analysis in which the configuration of the devices and some rock and fluids properties were changed. Additionally, the effect of the horizontal well length was studied as this parameter is relevant in the design and planning of horizontal wells in the Faja.
The results of this investigation indicated that the use of inflow control devices can be an effective technology to delay water breakthrough in areas where there is an active bottom aquifer with a good understanding of the geological properties and reservoir behavior. On other hand, this study showed how the differential increase in the cumulative oil of the wells decreases progressively as the horizontal well length section increases. An economic model was created to compare the different simulation scenarios.
This research serves as a basis for determining the feasibility of implementing inflow control devices as a water control technology and to obtain valuable information to designing the horizontal section of the wells.
Fault Trap Modelling and Calculation of Reserves
Authors: Zhang Xiaomin , Zhang Libin , Sun Desheng , Lin Jixiang , Kang Haixia 
Published: March 2015

Abstract
The evaluation of fault sealing is an important step in the calculation of fault trap reserve. When it comes to the issue of complex 3-D fault trap structures and thin reservoirs, how to appraise and calculate the reserve properly and effectively is still a subject that needs further researching. In this respect, a certain rift basin that has experienced multi-periods rift movement and evolved in a fluvial faces and braided deltaic depositional environment has been chosen as the object of our research on fault trap evaluation and calculation of reserves. The method has been preformed in the following steps. 1) The tectonic evolution and the structural characteristics of the studying area are accomplished through 3-D seismic interpretation; 2) Based on the results of the well to seismic combination, the provenance direction sedimentary system interpretation and sedimentary evolution are completed; 3) On the basis of achievements of the tectonic evolution and sedimentary evolution interpretation, the 3-D fault trap geologic model is established by spatial interpolation. A certain method invented by Li Qingzhong is employed to forecast the fault trap reserves quantitatively. Moreover, this method can be described as follows. Constrained by the seismic horizons, fault data and sedimentary isochronous interfaces, the connected sand body units in every depth slice of the 3-D fault trap geologic model can be identified automatically. Meanwhile, their sealing degree and connectivity is appraised quantitively from the top slice to the bottom slice. Finally, through quantitative calculation of reserves for fault trap, the effective forecasting of reserves has been achieved. The results of our work have testified that this appraisal method can be applied to improve the prospecting accuracy and reserve forecasting precision of fault trap reservoirs.
Successful Application of Unique Polyamine High Performance WaterBased Drilling Fluid in Bohai Bay Shale Formations
Authors: Hanyi Zhong , Zhengsong Qiu , Weian Huang , Jie Cao , Daquan Huang , Haibin Li 
Published: March 2015

Abstract
With the increasing demand of oil and gas resources, the drilled formations are becoming more and more complicated. Nevertheless, in the process of developing these hydrocarbon resources, wellbore instability caused by active shale hydration and dispersion is always a great challenge around the world. Therefore, it is necessary to develop a high performance water-based drilling fluid reaching into the property realm of oil-based drilling fluid but also environmentally acceptable.
This paper detailed the inhibitive properties of a novel polyamine shale hydration inhibitor SDJA-1 through bentonite inhibition test, cuttings hot-rolling dispersion test, bulk hardness test and X-ray diffraction analysis. The results show that polyamine is highly inhibitive and high temperature resistant, superior to conventional shale inhibitors.
Incorporated with shale encapsulator and lubricator, a polyamine high performance water-based drilling fluid was established based on triple inhibition. Extensive laboratory work was carried out to compare the properties of the system with other conventional inhibitive water-based drilling fluids and oil-based fluid. The results indicate that the system is highly inhibitive, rheology stable and excellently lubricant, approaching to the general oil-based drilling fluid.
Drilling in Bohai bay presents some unique challenges primarily related to wellbore instability in drilling through the highly complicated and reactive shale formations. Therefore the uniquely engineered polyamine high performance water-based drilling fluid was proposed with a special emphasis on wellbore stability. Three wells trials demonstrate that the system impart excellent performance like shale stability, trouble-free trips, and rheology stability. No bit balling is observed and ROP is improved compared to before. In conclusion, the system shows outstanding performance in all aspects and contributes to a high degree of success.
Drilling Risk Management in Offshore China: Insights and Lessons Learned from the Deepwater Horizon Incident
Authors: Cheng Rongchao , Wang Haige , Shi Li , Ge Yunhua , Sun Zhengchun , Tian Hongliang 
Published: March 2015

Abstract
The Deepwater Horizon disaster is undoubtedly verified as the most severe and systematic failure within the oil and gas industry to date, leaving a lasting legacy with enormous human, economic and environmental consequences. In the wake of this tragedy, CNOOC, Sinopec and CNPC are triggered with joint efforts to upgrade safety rules for shallow and deep water drilling, so as to keep up with increasingly risky operations in an increasingly tough situation in China. Especially, there is a pressing need to rebuild integrated strategy and reshape the future of offshore play in South China Sea, the major and prospective deepwater area typically featuring in HPHT and lacking of matched drilling risk control technologies.
Rigorous requirements are primarily analyzed with respect to present status of offshore drilling in China. All recorded oil spill incidents in GOM are statistically discussed to recognize controllable and uncontrollable reasons. Then, in view of the possible causes of the Deepwater Horizon accident, an integrated drilling risk management system was proposed with in-depth analysis in terms of six rules.
The primary and fundamental rule is to improve offshore drilling technology, including pressure control, wellbore profile design and adjustment, casing running, cementing, risk prediction and treatment, as well as related equipments like BOP, ROV and riser. The second is to further modify offshore drilling standards, specifications and regulations. The third is to strengthen supervision and management from both national and corporate structures. The fourth is to cultivate and intensify the safety culture within the whole drilling system. The fifth, also the most urgent, is to establish allied emergency response system for blowout, explosion and oil spill. The last is about recruiting, training and talent introduction.
The main purpose of this paper is to establish a specific drilling risk management system appropriate for offshore China to guarantee the energy security in the post-Macondo offshore play.
Seismic Data Driven Rock Physics Models and the Application to Tight Gas Saturation Estimation
Authors: Cao Hong , Yang Zhifang , Liu Jiawei , Tang Gang 
Published: March 2015

Abstract
Pore fluids prediction using seismic data is seldom covered in most considerable discussion in tight gas, although more interests are focused on fractures and sweet spots. Some theories based on homogeneous high porosity and permeability rocks have been widely investigated. Unfortunately, there seems to be no models published can properly describe the nonlinear relationship between saturation and P wave velocity at seismic frequency in tight reservoir, and low frequency experimental data are still scarce.
Gases always tend to gather at upper pore spaces in reservoir, resulting in saturation variation with depth due to interaction principle between buoyancy and capillary pressure. This law hence encourages us to probe into partial saturation related elastic properties through seismic data mining incorporating with experimental and logging data to indicate fluids.
Through various gas intervals oriented P wave-'saturation' data collections extracted from seismic data, new nonlinear relations are discovered, which indicate coexistence of patchy and homogeneous fluids effects, and cannot be properly explained by published models. Motivated by the complex relations of Vp-Sw at seismic frequency, a modified White's model is proposed to explain partial saturation effects in tight rocks, and updated rock physics models match the real seismic data quite well.
Case study of tight gas exploration in a Triassic basin in southwest China shows that seismic data-driven models are helpful means to reduce uncertainly in seismic interpretation and have improved the success rate of drilling by 20%.