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41.
Hydraulic fracturing is an important technique used for developing shale gas reservoirs. Compared with multistage consecutive fracturing, multistage alternative fracturing is a more challenging technique due to the current limitations of downhole tools. This paper simulates multistage fracturing and compares the fracture geometries and fluid distributions of consecutive and alternative fracturing. It is found that simultaneous propagation of multiple fractures results in their unequal stimulations. Some perforations do not contribute to well production because their fractures are restrained. Alternative fracturing tends to create more uniform length fractures and thus achieves a greater stimulated reservoir volume than that of consecutive fracturing. 相似文献
42.
Weifeng Ge Mian Chen Yan Jin Fuxiang Zhang Yunhu Lu Pei Yang Jihui Ding Hao Zeng 《Rock Mechanics and Rock Engineering》2011,44(6):711-723
To alleviate the problems of casing collapse induced by the coupling effect of salt creep movement, as it relates to the curved
sections of horizontal wells, an experimental approach was taken to determine the creep (visco-elastic) property of the salt-gypsum
formation, using finite-difference software to establish a creep model with curved casing, wellbore and salt formation. With
this model, the effects of borehole curvature, drilling direction and casing thickness on external pressure on casing were
analyzed, and casing deformation in the non-uniform in situ stress field was simulated. For horizontal wells drilled through
salt-gypsum formations, this analysis led to the following conclusions: (1) the casing tends to be much safer when drilling
is undertaken along the direction of the minimum horizontal stress; (2) casing deformation occurs and stress increases as
the borehole curvature increases; (3) for the same curvature and drilling direction, thicker casings are safer; (4) as the
creep time increases, the external pressure on the casing rapidly increases until it reaches its maximum value, whereupon
it stays at that value; (5) under the effect of non-uniform in situ stress, a larger non-uniform coefficient would result
in greater external pressure on the casing. This model has been successfully applied to analyze the external pressure on curved
casings in a build-up section for horizontal wells drilled through salt-gypsum formations in an oilfield in Northwest China.
The model has helped to improve the casing design and reduce drilling downtime with greater wellbore stability in salt-gypsum
formations. 相似文献
43.
Earth observation (EO)-based mapping and analysis of natural hazards plays a critical role in various aspects of post-disaster aid management. Spatial very high-resolution Earth observation data provide important information for managing post-tsunami activities on devastated land and monitoring re-cultivation and reconstruction. The automatic and fast use of high-resolution EO data for rapid mapping is, however, complicated by high spectral variability in densely populated urban areas and unpredictable textural and spectral land-surface changes. The present paper presents the results of the SENDAI project, which developed an automatic post-tsunami flood-extent modelling concept using RapidEye multispectral satellite data and ASTER Global Digital Elevation Model Version 2 (GDEM V2) data of the eastern coast of Japan (captured after the Tohoku earthquake). In this paper, the authors developed both a bathtub-modelling approach and a cost-distance approach, and integrated the roughness parameters of different land-use types to increase the accuracy of flood-extent modelling. Overall, the accuracy of the developed models reached 87–92%, depending on the analysed test site. The flood-modelling approach was explained and results were compared with published approaches. We came to the conclusion that the cost-factor-based approach reaches accuracy comparable to published results from hydrological modelling. However the proposed cost-factor approach is based on a much simpler dataset, which is available globally. 相似文献
44.
《Chemical Geology》2007,236(1-2):75-91
We remodel the annealing kinetics of fission tracks (FTs) in zircon to fit data from 43 laboratory experiments in three earlier publications using spontaneous FT lengths in zircon from the Nisatai Dacite. Heating temperature and time are in the ranges of 350–912 °C and 10− 3–104 h, respectively. The data sets illustrate a transition in annealing process at a certain temperature zone. In order to express the annealing behavior involving the possible transitional process with improved goodness of fit, two types of models are constructed; the hybrid-linear model that consists of the fanning-linear model at high temperature and the parallel-linear model at low temperature, connected with a transitional temperature zone, and the parallel-curvilinear model that approximates smoothly the transition in the annealing process. The validity of the extrapolation of the model to geological time scale is confirmed by comparison with some deep borehole core data. The length estimates by the hybrid-linear model agree well with the borehole data, whilst the estimates by the parallel-curvilinear model show a significant disagreement with highly annealed borehole samples although this model provides good agreement with the experimental data. For the hybrid-linear model, estimates of the partial annealing zone corresponding to isothermal heating for 106 and 107 years are 281–352 °C and 262–330 °C where the top and bottom of the partial annealing zone are defined by the mean length reduction ratio of 0.4 and 0.8, respectively. 相似文献
45.
DC (direct current) electrical and shallow seismic methods are indispensable to the near surface geophysical exploration, but the near surface areas are very difficult environments for any geophysical exploration due to the random noise caused by near surface inhomogeneities. As a new algorithm based on higher-order statistics theory, the higher-order correlation stacking algorithm for seismic data smoothing in the wavelet domain has been developed and applied efficiently to filter some correlation noise that the conventional second-order correlation stacking could not inhibit. In this paper, this higher-order statistics correlation stacking technology is presented for DC electrical data in wavelet domain. Taking into account the single section and multiple section data, we present two new formulations of correlation stacking for DC electrical data. Synthetic examples with Gaussian noise are designed to analyze the overall efficiency of the new algorithm and to determine its efficacy. Meanwhile, comparison with the traditional least-squares optimization inversion method for field examples from electrical imaging surveys and time-domain IP measurement in China shows its significant advantages. The quality of the new algorithm also has been assessed by physical simulation experiments. This new technology in DC electrical exploration measurements provides a new application in engineering and mining investigation. 相似文献
46.
In conventional studies of tracing dolomitization and diagenetic fluids, REEs of dolomites were widely used as been normalized by PAAS, NASC or chondrite. However, most dolomites are formed in seawater or seawater-derived fluids. Thus, we conduct a new attempt to normalize the REEs of dolomite using seawater standard, based on case studies on 36 Triassic limestone–dolomite samples from the Geshan section of southeast China and 26 Permian–Triassic dolomite samples from the Panlongdong section of northeastern Sichuan Basin, southwest China.The Geshan seawater-normalized (SN) REE patterns are characterized by notable positive CeSN (average CeSN/Ce* = 6.823, SD = 0.192) and negative PrSN anomalies (average PrSN/Pr* = 0.310, SD = 0.010), and slightly negative GdSN anomalis (average GdSN/Gd* = 0.864, SD = 0.053), with no obvious EuSN anomaly (average EuSN/Eu* = 1.036, SD = 0.094). The signatures of REE patterns barely changed during the dolomitization process. For the REE compositions of the Panlongdong dolomite, it can be found that (1) the recrystallization process can result in varied total REE concentrations (between 7.16 ppm and 37.87 ppm), but do not alter the REE patterns, including consistent positive CeSN anomalies (average = 4.074, SD = 0.27) and LREE enrichment (average NdSN/YbSN = 3.164, SD = 0.787); (2) meteoric incursion can reverse Ce anomaly, from the strong positive Ce anomalies (CeSN/Ce* = 5.059) to slightly positive (CeSN/Ce* = 2.459) or even negative Ce anomalies; and (3) hydrothermal fluid altered REE pattern is complicated by fluctuated distribution curve, negative Ce anomaly and positive Eu anomaly (EuSN/Eu* = 1.862). These results suggest that the seawater normalized REE patterns of dolomite can serve as an index to study the source of the dolomitization fluids and distinguish complex diagenetic processes, providing a complement to previous works. 相似文献
47.
The first exploratory well, the ZS1C well, with 158,545 m3 daily gas production was discovered in 6861–6944 m deep strata of the Cambrian gypsolyte layer of the Tarim Basin, China in 2014. The discovery opens a new target for the Cambrian-reservoired oil and gas exploration, and directly leads to large-scale oil and gas exploration of the deep-reservoired Cambrian oil and gas fields in the Basin. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry and a comprehensive two-dimensional gas chromatography–flame ionization detector revealed the presence of abundant adamantane compounds, 2-thiaadamantanes and 2-thiadiamantanes, and a large amount of sulfur-containing compounds in the condensate oil. The formation of organic sulfur-containing compounds, such as 2-thiaadamantanes, is an indication of sulfur incorporation from the gypsum in the stratum into oil and gas in the course of TSR. This reservoir has apparently suffered severe TSR alteration because (1) High content of H2S, (2) H2S sulfur isotopes, (3) CO2 carbon isotopes, and others abundant data to support this findings. Similar sulfur isotopic composition of H2S, oil condensate and the gypsum in the Cambrian strata indicate that the produced condensate is experienced TSR alteration. Therefore, the deep-accumulated Cambrian oil reservoir has experienced severe TSR alteration, and accumulated natural gas and condensate contains high sulfur content. 相似文献
48.
The Ordovician is the most important exploration target in the Tabei Uplift of the Tarim Basin, which contains a range of petroleum types including solid bitumen, heavy oil, light oil, condensate, wet gas and dry gas. The density of the black oils ranges from 0.81 g/cm3 to 1.01 g/cm3 (20 °C) and gas oil ratio (GOR) ranges from 4 m3/m3 to 9300 m3/m3. Oil-source correlations established that most of the oils were derived from the Mid-Upper Ordovician marine shale and carbonate and that the difference in oil properties is mainly attributed to hydrocarbon alteration and multi-stage accumulation. In the Tabei Uplift, there were three main periods of hydrocarbon accumulation in the late Caledonian stage (ca. 450–430 Ma), late Hercynian stage (ca. 293–255 Ma) and the late Himalayan stage (ca. 12–2 Ma). The oil charging events mainly occurred in the late Caledonian and late Hercynian stage, while gas charging occurred in the late Hercynian stage. During the late Caledonian stage, petroleum charged the reservoirs lying east of the uplift. However, due to a crustal uplifting episode in the early Hercynian (ca. 386–372 Ma), most of the hydrocarbons were transformed by processes such as biodegradation, resulting in residual solid bitumen in the fractures of the reservoirs. During the late Hercynian Stage, a major episode of oil charging into Ordovician reservoirs took place. Subsequent crustal uplift and severe alteration by biodegradation in the west-central Basin resulted in heavy oil formation. Since the late Himalayan stage when rapid subsidence of the crust occurred, the oil residing in reservoirs was exposed to high temperature cracking conditions resulting in the production of gas and charged from the southeast further altering the pre-existing oils in the eastern reservoirs. A suite of representative samples of various crude oils including condensates, lights oils and heavy oils have been collected for detailed analysis to investigate the mechanism of formation. Based on the research it was concluded that the diversity of hydrocarbon physical and chemical properties in the Tabei Uplift was mainly attributable to the processes of biodegradation and gas washing. The understanding of the processes is very helpful to predict the spatial distribution of hydrocarbon in the Tabei Uplift and provides a reference case study for other areas. 相似文献