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Collaborating Authors
Yu, Gang
ABSTRACT An integrated study of the well Zhao-104 and surrounding wide-azimuth 3D seismic volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. The inversion for P and S impedance and derivative attributes produced volumes that relate to rock properties such as brittleness and rigidity that are likely to impact fracturing. Seismic attribute analysis of anisotropy from elliptical velocity inversion indicates that anisotropy varies horizontally and vertically, and that it is dominantly controlled by stress azimuth, which conforms to the current day stress field as independently determined from borehole break-outs. Presentation Date: Tuesday, October 18, 2016 Start Time: 11:10:00 AM Location: 155 Presentation Type: ORAL
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline > Geomechanics (0.93)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (1.00)
Summary An integrated study of the well Zhao-104 and surrounding wide-azimuth 3D seismic volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. The inversion for P and S impedance and derivative attributes produced volumes that relate to rock properties such as brittleness and rigidity that are likely to impact fracturing. Seismic attribute analysis of anisotropy from elliptical velocity inversion indicates that anisotropy varies horizontally and vertically, and that it is dominantly controlled by stress azimuth, which conforms to the current day stress field as independently determined from borehole breakouts. Introduction An integrated study of the well Zhao-104 and surrounding wide-azimuth 3D seismic data volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. Well data, structural seismic information and prestack inversion products were combined in an integrated interpretation. Seismic gather conditioning improved seismic data quality prior to prestack inversion by improving signal/noise ratio, removing NMO stretch and aligning reflection events. Velocities from residual moveout (RMO) analysis on individual sectors were used as input to detection of fracture orientation and anisotropy. Fracture strike and P wave anisotropy were calculated using the RMO updated sector velocity fields in elliptical velocity inversion, while inversion for P and S impedance and derivative attributes produced volumes that relate to rock properties such as brittleness and rigidity that are likely to impact fracturing. Inversion of seismic data During the prestack inversion process, the velocity field was updated after residual moveout analysis for each sector and used in elliptical velocity inversion to determine degree and direction of anisotropy.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (1.00)
Distributed acoustic sensing (DAS) is a novel technology that uses an optical fiber cable as a sensor for acoustic signals and can take almost any downhole fiber-optic installation or deployment and turn the fiber-optic cable into a large downhole seismic array. This array can provide enhanced vertical seismic profile (VSP) imaging and monitor fluids and pressure changes in the hydrocarbon-production reservoir. Walkaway VSP data acquired over a formerly producing well in northeastern China provided a rich set of high-quality DAS walkaway VSP data. A standard VSP data preprocessing workflow was applied, followed by prestack Kirchhoff time migration. In the DAS preprocessing step, we were faced with additional challenges: strong coherent noise due to cable slapping and ringing along the borehole casing. Compared with an earlier offset VSP data set using 327 levels acquired with conventional 3C downhole geophones in the same well, the final preprocessed DAS walkaway VSP has a larger vertical aperture, resulting in a wider lateral image. The single-well DAS walkaway VSP images provide a good result with higher vertical and lateral resolution than the surface seismic in the objective area. The vertical-well environment, which lacks the ability to effectively โclampโ the sensor to the borehole-casing wall by touching, creates a unique set of challenges. Although earth signal was recorded with almost all the shots, there was also a considerable amount of noise. Much of the noise was due to the physical placement of the wireline in the well and was expressed by slapping and ringing. Reported here are lessons learned in handling the wireline cable and subsequent special DAS data processing steps developed to remediate some of the practical wireline deployment issues. Optical wireline cable as a conveyance of fiber-optic cables for VSP in vertical wells will open the use of the DAS system to wider applications.
Laboratory Study on High-performance Lightweight Cement Slurries for Thermal Production Wells
Zeng, Jianguo (Tianjin Bo-Xing Engineering Science & Technology Limited Company of CNPC) | Yu, Gang (Tarim Oilfield Branch Company of PetroChina) | Liu, Aiping (Tianjin Bo-Xing Engineering Science & Technology Limited Company of CNPC) | Sun, Fuquan (Tianjin Bo-Xing Engineering Science & Technology Limited Company of CNPC) | Xia, Yuanbo (Tianjin Bo-Xing Engineering Science & Technology Limited Company of CNPC) | Li, Pengxiao (Tianjin Bo-Xing Engineering Science & Technology Limited Company of CNPC) | Yuan, Zhongtao (Tarim Oilfield Branch Company of PetroChina)
Abstract The main challenging cement shiny problems, such as weak formation with the pressure gradient of about 1.60g/cm3, non-retrogressive compressive strength at 240 ยฐC in steam stimulation and fast compressive strength development at about 18ยฐC in the wellhead, have been encountered in thermal production wells. To answer these challenges, the high-temperature resistant lightweight cement slurries with the densities of 1.40g/cm3 and 1.50g/cm3 were designed by choosing density reducer cenosphere and applying the high packing theory. These additives, such as retarder, fluid loss additive and accelerator, were also developed. The rheology, API fluid loss, compressive strength, free water and compressive strength stability in 240ยฐC were researched as well. The result showed that the properties of the cement slurries meet the need of the cementing job at 50ยฐC. The compressive strength on the top of the lightweight cement slurry column was more than 3.5MPa after curing for 36h at 18 ยฐC. The compressive strength was more than 30M4Pa and did not regress after curing for 28d at 240 ยฐC. The properties of the high-performance lightweight cement slurries could meet the requirements of the thermal production wells at 240ยฐC. Introduction Both the China's increasing demand for energy and the decline of traditional oil and gas reserves have forced operators to go after unconventional resources. As an abundant and important unconventional resource, heavy oil could be an answer to the demand for energy. Thermal recovery technology, the most effective heavy oil exploitation way, is currently the largest and most mature applied FOR techniques of the world. The technology predominantly via steam huff and puff also with continuously applied steam flooding, electric heating and SAGD technology could benefit 1500 ร104 tons of oil every year in China (Wang, 2010). The main challenging cement slurry problems, such as weak formation with the pressure gradient of about 1.60g/cm, non-retrogressive compressive strength at 230ยฐ C. in steam stimulation and fast compressive strength development at about 18ยฐC in the wellhead, have been encountered in thermal production wells. The conventional lightweight cement slurries, however, usually developed low and retrogressive compressive strength, which limits their applications in cementing for heavy-oil reservoirs. In order to cope with these challenges, the high-tolerant lightweight cement slurries for 232ยฐC steam huff and puff of the thermal production wells, based on concept of high packing density, were invented by Schlumberger Oilfield Services in the late 20 century [Biosnault, 1999 and Al-Suwaidi, 2001]. In this paper, high-performance lightweight cement slurries for thermal production wells with the densities of 1.40g/cm and 1.50g/cm have been developed based on high-packing theory. The long-term compressive strength of set cements at 240ยฐC was also investigated.
Fluid Characterization with LWD Resistivity and Capture Cross Section Enhances Understanding of Horizontal Well Production โ A Case Study in a Siliciclastic Brownfield
Liu, Ruiying (Tarim Oil Company) | Li, Qiang (Tarim Oil Company) | Li, Ting (Schlumberger) | Liu, Yanmei (Schlumberger) | Lu, Zhongyuan (Tarim Oil Company) | Yu, Gang (Tarim Oil Company) | Guo, Xinyong (Tarim Oil Company) | Yang, Chuan (Tarim Oil Company)
Abstract In this case study, we examine oil wells in a brownfield, where water production is a major concern. The target reservoirs consist of several thin sandstone beds with excellent lateral extension. As a result, the operator generally chooses to produce from long horizontal sections. In order to better understand production and make informed decision about future development plans, it is critical for the operator to accurately characterize fluids in the field through well logging. The challenge in formation evaluation lies in the uncertainty in formation salinity, because the injected water makes formation water salinity highly variable. In such environments, saturation equations that rely on a good knowledge of the water salinity, such as resistivity-based equations (Archie) or ther mal neutron capture cross section (Sigma), cannot fully capture the variability in fluids distribution in the reservoir. The problem is further complicated by low-resistivity-pay, where the resistivity contrast between water and pay zones is quite small. A recently proposed workflow can solve for water salinity at each depth level by simultaneously inverting for water saturation (Sw) and water resistivity (Rw) from resistivity and Sigma logs. This method does not require a priori knowledge of water salinity. One can further compute an irreducible water saturation (Swi) from lithological dry weights, which in turn are derived from geochemical logs. The amount of water that's movable in the pore space is then given by Sw โ Swi. We can use Sw โ Swi as a qualitative indicator of water floods distribution and use it to understand fluids production of horizontal wells and design the next phase of development to target bypassed hydrocarbon. In this report, we studied the LWD logs and production history of 3 horizontal wells in a brownfield, where formation salinity is highly variable. It is found that water production is directly related to Sw โ Swi. We also show that resistivity-based saturation equations can give misleading interpretation of the fluid type due to variable salinity. Adding Sigma into the interpretation model accounts for salinity changes and gives results that are consistent with production history.
- North America > United States > Texas (0.28)
- Europe (0.28)
Abstract Borehole-to-surface time-frequency domain electromagnetic (TFEM) method has been applied in delineating oil/gas and water boundary. The technique has achieved significant improvements over the past 10 years and has become an important technique for oilfield development. Recently this method has been applied in a newly found oil and gas target in a mountainous area in the western plateau of China. Due to the complexity of the oilfield development area, some new technical measures have been taken when using the TFEM technique, such as multi-well joint operation program, multi-source excitement for multi-target layers, terrain correction, and then extracting effective induced polarization anomalies and high resistivity anomalies through dual frequency amplitude and tri-band phase anomaly. Drilling results have confirmed the effectiveness of the borehole-to-surface TFEM method in this oilfield. Based on the integrated interpretation result, confirmed oil-bearing areas within the oilfield are enlarged and provided very important basis for the selection of hydrocarbon reservoir delineation wells. The borehole-to-surface TFEM survey results show that joint operation program of multiple source wells can evaluate relatively large area of traps. Multiple downhole source positions and graded source excitation can be used for detecting multi-target layers. A simple data processing method can depress terrain's effect, and then the high polarization anomalies and high resistivity anomalies reflecting hydrocarbon reservoirs are effectively extracted using the dual frequency amplitude anomaly and tri-band phase anomaly. Finally, potential hydrocarbon accumulation areas can be effectively evaluated and mapped. Drilling results have confirmed the validity of the method and this method provides an effective means for the delineation of hydrocarbon boundary and the selection of evaluation wells in newly developing oilfields.
- Asia > Middle East (0.47)
- Asia > China (0.36)
- Research Report > New Finding (0.35)
- Research Report > Experimental Study (0.35)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (0.98)
- Geophysics > Electromagnetic Surveying > Borehole Electromagnetic Surveying (0.32)
Summary Electromagnetic method is one of the important approaches to hydrocarbon prospecting. This paper describes an approach to invert resistivity and induced polarization (IP) using the combined constrain of seismic and electric logging data. As a result, the accurancy of hydrocarbon reservoir distribution prediction based on formationโs electrical properties is significantly improved. The paper presents an example illustrating that joint constrained inversion and integrated interpretation workflow of electromagnetic properties (resistivity and polarization), seismic traps as well as seismic attributes, can significantly reduce drilling risks for oil and gas exploration. The statistic number on practical projects also supports the conclusion. The paper also discussed how the joint inversion and interpretation workflow works at different stages of oil and gas exploration and production with very positive results. Introduction We understand that hydrocarbon reservoir distrrbution is controlled by many factors, including complex surface and underground conditions. Reservoirs have different types, such as structural reservoir, lithologic reservoir, and stratigraphic reservoir (Niu, et al., 2005). Drilling risks exist not only due to the above factors, but also because of the fluid movement and variation of oil, gas and water during production period. Therefore, any single geophysical method cannot completely eliminate drilling risk (Xiong, 1997). Electromagnetic (EM) method is given more expectation on the prediction of subsurface oil, gas and water distribution (He and Wang, 2002; He, et al., 2010). However, due to its low resolution on underground targets, surface EM methods have not been widely applied within oil and gas industry. While for wireline logging or MWD/LWD, EM method is one of the major approaches to distinguish oil, gas and water. It is well known that resistivity is the most frequently used parameter for hydrocarbon layer interpretation in all logging parameters. Yearsโ experience indicates that resistivity is related to oil, gas and water saturation in the reservpor formation rock pore space. Higher oil or gas saturation usually leads to higher resistivity (Xiao and Xu, 2006). Therefore, resistivity anomaly can be used to predict and interpret hydrocarbon-bearing possibility in the subsurface formation. Recent years, another parameter, induced polarization (IP), has gained more and more attentions. Induced polarization (IP) log has been applied for oil or gas interpretation within logging industry. Many laboratory tests and oilfield tests show that high oil or gas saturation is strongly associated with high induced polarization. Oilsaturated rocks are tested to study the low frequency resistivity dispersion effect, mainly caused by the IP effect. The tests indicate that IP effect becomes stronger when oil and gas saturation increased (Xiao and Xu, 2006).
- Geology > Geological Subdiscipline > Stratigraphy (0.54)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.48)
- Geology > Petroleum Play Type > Conventional Play > Structural Play (0.34)
- Geophysics > Electromagnetic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (0.69)
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.48)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin (0.99)
- Asia > China > Qinghai > Qaidam Basin (0.99)
- North America > United States > Louisiana > China Field (0.97)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
Summary Our study applied a geophysical well log analysis, rock physics diagnostics and rock physics modelling to an exploration well log data from a shale gas exploration area in the Sichuan Basin of South China. The study established an unconsolidated model (80% quartz plus 20% clay in the shale gas formation) transform between the acoustic and elastic impedance on the one hand and lithology, porosity, water saturation, clay content, quartz content, and TOC content on the other hand. Through our geophysical well log analysis, we calculated mineral volumes using best available data, total and effective porosity, water saturation, and bulk density and VS prediction where it was missing. For rock physics modeling, the shale gas formation matrix substitution (Clay, Quartz and TOC) and porosity modeling were performed in this exploration well. Crossplots are also used to analyze the elastic properties of the shale gas formation including VP velocity vs density, Acoustic Impedance (AI) vs total porosity (FT), AI vs Poissonโs Ratio (PR), and VP vs VS. The results were quality controlled by core sample laboratory analysis data. To understand seismic effect as a result of rock physics modeling, ray traced synthetic modelling has been applied. The Ray-traced synthetics have been generated for the in situ and modeled scenarios for AVA analysis. These transforms will be upscaled and applied to acoustic and elastic impedance inversion volumes to map lithology, porosity, and TOC distribution in the shale gas exploration area. Introduction The characterization of shale gas formation is rapidly gaining prominence as a result of the increasingly important role of unconventional reservoirs in South China. Engineering practices such as horizontal drilling and hydraulic fracturing in shale gas formation has created a need for volumetric quantification not only of fracturing but of other geomechanical properties such as Youngโs Modulus, Poissonโs Ratio, and maximum horizontal stress direction, in addition to more conventional reservoir properties such as lithology, brittleness, TOC and porosity as input for reservoir simulations
- Europe > Norway > Norwegian Sea (0.25)
- Asia > China > Sichuan Province (0.25)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Mineral (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling (0.69)
Summary An integrated study of the well Zhao-104 and surrounding seismic volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. Seismic attribute analysis of anisotropy from elliptical velocity inversion indicates that anisotropy varies horizontally and vertically, and that it is dominantly controlled by stress azimuth, which conforms to the current day stress field as independently determined from borehole break-outs. For the reservoir, it appears that the modernโday SH (N40E) orientation approximates the conjugate fracture orientation of a wrench-faulted tectonic regime; this map pattern suggests a clockwise net rotation of the stress field from time of deposition to the present-day by 40ยฐ. Very large strike-slip faults (cutting the survey) have low anisotropy. Intermediate strike-slip faults cutting the entire shale section may exhibit larger anisotropy. Structural depressions formed by transtension act as TOC-rich sinks and likewise feature large anisotropy vectors. Relative paleo-sea-level change influenced mineral assemblages and elastic properties of systems tracts. Of several interpreted transgressions, only the first transgressive phase is associated with significant TOC-deposition. INTRODUCTION An integrated study of the well Zhao-104 and surrounding seismic volume within the shale gas reservoir in South China has been conducted with the objective of generating shale formation properties related to fracture orientation and intensity in the area and deriving such reservoir rock properties as data quality allows. Well data, structural seismic information and prestack inversion products were combined in an integrated interpretation.
- Asia > China (0.56)
- North America > Canada > Alberta (0.16)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (0.56)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
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Application of Wide-Azimuth 3D Seismic Attributes to Predict the Microfractures in Block MA Area for Shale Gas Exploration in South China
Zhang, Yusheng (BGP, CNPC, P. R. China) | Yu, Gang (BGP, CNPC, P. R. China) | Liang, Xing (Zhengjiang Oilfield, CNPC, P. R. China) | Jiang, Li (RSI, Houston, USA)
Summary It is key for the success of the Paleozoic marine shale gas exploration and development in South China to search for the sweet spots or shale gas-rich zones within the shale gas reservoir. Since it directly impacts the shale gas enrichment degree and hydro-fracturing effect of the shale gas reservoir, the development degree of shale gas reservoir fractures is the important factor for the prediction and evaluation of the sweet spots or shale gas-rich zones. This paper proposes a seismic fracture facies evaluation workflow for shale gas reservoirs and its application through the utilization of 100 km wide-azimuth 3D seismic data post stack attributes in the Block MA shale gas exploration area. We focus especially on using neural network techniques to analyze the 3D seismic attribute data for fracture prediction. The examples show that using the technique could play an important role in the prediction and assessment of the gas-rich zones in shale gas reservoirs.
- Asia > China > Sichuan > Sichuan Basin (0.99)
- North America > United States > Texas > East Gulf Coast Tertiary Basin > South China Field (0.95)