A Bingham-Plastic Model for Fluid Mud Transport Under Waves and Currents

Simplified equations of fluid mud motion, which is described as Bingham-Plastic model under waves and currents, are presented by order analysis. The simplified equations are non-linear ordinary differential equations which are solved by hybrid numerical-analytical technique. As the computational cost is very low, the effects of wave current parameters and fluid mud properties on the transportation velocity of the fluid mud are studied systematically. It is found that the fluid mud can move toward one direction even if the shear stress acting on the fluid mud bed is much smaller than the fluid mud yield stress under the condition of wave and current coexistence. Experiments of the fluid mud motion under current with fluctuation water surface are carried out. The fluid mud transportation velocity predicted by the presented mathematical model can roughly match that measured in experiments.

In-Situ Observation of Fluid Mud in the North Passage of Yangtze Estuary, China

Observations of fluid mud were made in the lower North Passage of the Yangtze Estuary in February 2000, on 10～11 August 2000, on 30～31 August 2000 (after two strong typhoons), on 21～24 August 2000 (neap tide) and on 3～6 September 2000 (mean tide) respectively. In situ data show that the fluid mud in this area consists of fine cohesive sediment (median size 7.23 μm). The formation and movement of fluid mud varied during the neap-spring and flood-ebb tidal cycle. Observations suggest that fluid mud phenomena in this area may be categorised in a three-fold manner as slack water, storm and saltwedge features. The thickness of the fluid mud layer of slack water during the neap tide ranged from 0.2 to 0.96 m, whereas during the mean tide, the thickness ranged from 0.17 to 0.73 m, and the thickness of the fluid mud layer was larger during slack water than at the flood peak. Shoals cover an area of 800 km2 with a water depth smaller than 5 m. Erosion of these extensive intertidal mudflats due to storm action provides an abundant sediment source. This is particularly significant in this estuary when the tidal level is lower than 5 m. The lower North Passage is a typical zone of saltwater wedging, so the saltwedge fluid mud has the most extensive spatial range in the estuary.

Fluid Mud Measurement and Siltation Analysis in A Trial Excavated Channel in the Approach Channel of the Xiangshan Port

In order to clarify the distribution and variation of silt and fluid mud in the Waiganmen shallow section of the 50000-ton intake channel of the Xiangshan Port,and to understand the influence of the channel excavation on the surrounding flow conditions and the strength of the backsilting,especially the impact of typhoon on the sudden silting of the channel,so as to demonstrate the feasibility and stability of the channel excavation.The fluid mud,hydraulic,sediment and topographic measurements were carried out in the study area,and the thickness of the fluid mud layers,tidal current,sediment and topographic data were obtained.Dual-frequency sounder,gamma-ray densitometer and SILAS navigational fluid mud measurement system were used to monitor the fluid mud,and the results were compared and verified.The adaptability and accuracy of the three methods were analyzed.The SILAS navigational continuous density measurement system and gamma-ray fixed-point fluid mud measurement are used to detect the density,thickness and variation of the fluid mud accurately.Based on the hydrological observation data,the process of erosion and deposition in excavation channel and its influence mechanism are analyzed,and the distribution characteristics and evolution law of siltation in engineering area are given in the form of empirical formula.The research shows that the super typhoon can produce large siltation,which results in sudden siltation of the channel.The tidal current is the main dynamic factor of the change of erosion and siltation of the excavation trench.Under the influence of reciprocating tidal current and excavation topography,the trial excavation trench is silted on the whole.There is fluid mud in the monitoring area of the trench,and the distribution of fluid mud is different in space.The thickness of the fluid mud at the bottom of the trench is generally larger than that outside the trench and the slope of the trench,and the siltation of the trench tends to be slow.The research results can provide scientific evaluation for channel excavation and maintenance,and support for the implementation of the project.

Geoacoustic model and acoustic reflection properties of fluid mud layer in Changjiang Estuary and Hangzhou Bay

A generalized geoacoustic model of fluid mud layer in Chanaiiang Estuary and Hangzhou Bay has been derived from a large amount of in-situ measurements of bulk density (p) profiles of the lay6rs and of lab measurements of acoustic velocities (c) and attenuation coefficients (o) of the fluid mud samples with different values of p for four frequencies of 100 kHz, 150 kHz, 500 kHz, 1500 kHz. The main features of the geoacoustic model can be expressed as follows: from the upper boundary, the bulk density of the fiuid mud increases linearly with depth z, however there is a gradient change (knee) when p is about 12.5 kN/m', then p increases linearly to a value about 15.0 kN/m'. After p more than 15.0, the fluid mud layer quickly transform into an ooze layer. In the fluid mud layer, the acoustic velocity c can be regarded as constant since its variation with z less than 1.5%, and a minimum vaue of c ekists when p is about 13.5 kN/m'. The variations of β with p and with frequency f are linear. Based on the geo-acoustic model and the ray theory, simulations of sound refiection from the fluid mud layers have been made, and some significallt results obtained, from which the bulk density profiles of fluld mud layers can be derived inversely.

Fluid mud transportation at water wedge in the Changjiang Estuary

In situ data show that fluid mud of the Changjiang Estuary consists of fine sediment ranging from 8 to 11.5 μm (median grain-size) including 28.8%-36.4% of clay. The composition of the clay is illite, chlorite, kaolinite and montmoillonite. The FM is a layer of high sediment concentration near the bed and results from flocculation under the environment of salt and fresh water mixing. Three kinds of FM have been identified under typical dynamic conditions: the first one is formed at slack water of ebb tide during the flood season, with the characteristics of extended area and low thickness; the second one is formed following a storm, characterized by large area and larger thickness; the third one is formed around the front of the saltwater wedge, characterized by small area but large thickness. In the dredged channel, the FM can be accumulated up to 1 m thick. In general, FM will change with the alternation from spring to neap tides, flood and dry seasons. Drastic change can happen during storms. At the same time, the change of FM is closely related to the erosion and growth of the mouth bar.

The instability of water-mud interface in viscous two-layer flow with large viscosity contrast

The temporal instability of parallel viscous two-phase mixing layers is extended to current-fluid mud by considering a composite error function velocity profile. The influence of viscosity ratio, Reynolds number, and Froude number on the instability of the system are discussed and a new phenomenon never discussed is investigated based on our numerical results. It is shown that viscosity can enlarge the unstable wave number range, cause new instability modes, and certainly reduce the growth rate of Kelvin-Helmholtz （K-H） instability.

A novel oil-in-water drilling mud formulated with extracts from Indian mango seed oil

Drilling muds with less environmental impact are highly desired over conventional diesel-based mud systems,especially in light of the emerging strict environmental laws.In this article,a novel oil-in-water(O/W)emulsion drilling fluid formulated with a methyl ester extracted from Indian mango seed oil was evaluated.The effect of the weight percent of different constituents of the emulsion/suspension including the oil phase,bentonite,and polyanionic cellulose polymer on the rheology and the fluid loss was examined.The methyl ester oil phase/mud system displayed superior physical,chemical,rheological and filtration properties relative to the diesel and the mango seed oil.Eco-toxicity of the methyl ester and diesel(O/W)emulsion mud systems was assessed using the acute lethal concentration test.The Indian mango methyl ester(O/W)emulsion mud displayed much less impact on fish population.Flow characteristics collected from the flow model at 85°C suggested excellent shear thinning behavior of the Indian mango methyl ester(IMME)(O/W)emulsion mud.Moreover,the IMME(O/W)emulsion displayed strong pseudoplastic behavior,an attractive feature in a drilling mud,with increasing clay content and polymer concentration.The methyl ester mud was thermally stable over a wide range of the constituent concentrations.Furthermore,a particle size analysis revealed that engineered drilling muds targeting suspension of particles with certain size range can be formulated by changing the volume fraction of the methyl ester in the mud system.

Experimental Investigation of Drilling Fluid Performance as Nanoparticles

In this work, a drilling fluid recipe has been developed by using nanoparticles, to increase the efficiency of drilling operations for maximum accessibility to new & matured oil reserves and suited to various drilling conditions. The solution to severe drilling problems like pipe sticking, lost circulation, formation damage, erosion of borehole, thermal instability of drilling fluids and insufficient gel properties of the drilling fluids, lies in controlling and optimizing the rheology of the drilling fluid. The inefficiency of the drilling fluid in performing certain functions is mainly due to a lack in a particular rheological property. The performance of the clay composites water-based bentonite drilling mud in terms of its rheological behavior in drilling systems was investigated at various pressures and temperatures. It was found that temperature had a detrimental effect on the rheological properties. The behavior was investigated using synthesized nano bentonite water based drilling fluid. The fluid retained all the desired rheological properties at elevated temperatures and pressures, thus enhanced the possibility of its application in deep wells, where elevated temperatures and pressures were quite common.

Mud volcanoes in the South Caspian basin: Nature and estimated depth of its products

In paper based on the results of previous studies and latest investigations of mud volcanoes in the South Caspian basin the depth occurrence of fluid, mud and rocks are calculated and modeled. Major factors causing formation of diapirism/mud volcanism in the South Caspian basin are Pliocene-Quaternary high sedimentation rates (up to 3 km/my), super thick sedimentary cover (up to 25-30 km), predominance of clayey rocks (reaching 80%) in the section, low temperatures (with 15℃-18℃/km gradient), overpressures reaching lithostatic, the onset of petroleum generation lowered to considerable depths. The majority of the mud volcanoes are associated with the petroleum bearing structures. Depths where the liquid, gaseous and solid products of mud volcanoes are sourced appear to be different. The gases have the deepest roots (7-15 km) which are the main force in formation and activity of MVs. Source of the fluidized clayey mass does not lie below 3-4 km. Oils emitted by mud volcanoes are the product of destruction of petroleum accumulations occurring beneath them.

THE WAVE ATTENUATION ON THE MUD BED

In the paper the wave attenuation in a two layer fluid system is studied.The fluid in the top layer is ideal and that in the lower layer is the Voigt model of the viscoelastic medium.A dispersion relation is derived and the rate of the wave decay is computed.The approximate explicit expressions of the decay rate for different water depth are given,where the viscoelasticity is either very large or very small.Compared with the numerical results,our results are very accurate,which can be used by an engineer.

Development of key additives for organoclay-free oil-based drilling mud and system performance evaluation

Traditional oil-based drilling muds(OBMs) have a relatively high solid content, which is detrimental to penetration rate increase and reservoir protection. Aimed at solving this problem, an organoclay-free OBM system was studied, the synthesis methods and functioning mechanism of key additives were introduced, and performance evaluation of the system was performed. The rheology modifier was prepared by reacting a dimer fatty acid with diethanolamine, the primary emulsifier was made by oxidation and addition reaction of fatty acids, the secondary emulsifier was made by amidation of a fatty acid, and finally the fluid loss additive of water-soluble acrylic resin was synthesized by introducing acrylic acid into styrene/butyl acrylate polymerization. The rheology modifier could enhance the attraction between droplets, particles in the emulsion via intermolecular hydrogen bonding and improve the shear stress by forming a three-dimensional network structure in the emulsion. Lab experimental results show that the organoclay-free OBM could tolerate temperatures up to 220 ?C and HTHP filtration is less than 5 m L. Compared with the traditional OBMs, the organoclay-free OBM has low plastic viscosity, high shear stress, high ratio of dynamic shear force to plastic viscosity and high permeability recovery, which are beneficial to penetration rate increase, hole cleaning and reservoir protection.

库区浮泥层纵向流速垂线分布特性研究

水库浮泥是存在于水库底部的一层高含沙水体,流动性较强,直接影响水库淤积形态和水库排沙,研究其运动规律对水库减淤优化调度具有重要意义。根据三峡库区实测泥沙矿物组成和级配资料,配置沙样进行流变试验,以幂律流变模型描述浮泥的本构关系。构建了浮泥运动的速度分布理论模型,通过水槽试验对模型进行了验证,计算结果与试验结果吻合较好。结果表明,浮泥运动速度随浮泥厚度、上层水流流速、床面坡度增大而增大,随浮泥密度增大而减少。沿水深方向浮泥纵向流速分布始终呈抛物线型,表层的浮泥流速要远大于底层浮泥,浮泥纵向流速沿垂向方向不断减少,最底部的浮泥几乎处于静止状态。

负压振动筛原理及在油基钻井液钻屑减量中的应用

经过几十年的发展,振动筛性能有很大提高,但其对钻屑的脱液能力已达极限。40年来,应用于钻井固控,效果不明显。十多年前,经过尝试与高频低幅振动相结合的真空过滤技术应用于钻井固控时,钻屑的脱液能力显著提高,排放钻屑体积大幅减小。近年来,多种负压振动筛在国内钻井中开展了应用试验。经过对常规振动筛复合负压过滤的负压振动筛的原理、主要技术参数、现场应用与国内外类似技术的对比分析及现场应用表明,所使用的负压振动筛的处理量、钻屑含液率、钻屑排放减少量、筛网寿命、能效、设备成本、使用经济效益等都均有明显优势。负压振动筛的应用对节能减排和实现“碳中和”具有重要作用,其逐渐替代常规振动筛,将是钻井固控技术发展的必然趋势。

A Review of Studies on the Interaction Between Waves and Muddy Bottom

This paper presents a brief review of the results on the interaction between waves and muddy bottom obtained during the last decade including the results obtained by the author at the Coastal Engineering Laboratory of Tianjin University.

Utilizing NMR Mud Logging Technology To Measure Reservoir Fundamental Parameters in Well Site

Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the fluid. NMR mud logging can measure drill cutting, core and sidewall core in the well site, also according to the experiment results, the sample type and size has little effect to analysis result. Through NMR logging, we can obtain several petrophysical parameters such as total porosity, effective porosity, permeability, oil saturation, water saturation, movable fluid saturation, movable oil saturation, movable water saturation, irreducible fluid saturation, irreducible oil saturation, irreducible water saturation, pore size and distribution in rock samples, etc. NMR mud logging has been used nearly 10 years in China, Sudan, Kazakhstan, etc. it plays an important role in the interpretation and evaluation of reservoir and its fluids.

Physical and chemical changes of water in the deep interior of the Earth―Decrepitation-style mud-volcano-earthquake―A bright lamp to shed light on the mysteries of the deep interior of the Earth

The 2008-05-12 Wenchuan mud-volcano-earthquake was accompanied with eruption of a huge volume of gas and stone,revealing that earthquakes generally result from instant reverse phase explosion of supercritical water(SCW) at the supercritical point.In the deep parts of the crust and mantle there still exists a large amount of supercritical water equivalent in order of magnitude to that of the Earth's hydrosphere.Soft fluids which exist in the MOHO at the top of the upper mantle are the so-called deep supercritical fluids(SCWD).Supercritical water(SCW) has n×103 times strong capability to dissolve gas.Its viscosity is extremely low and its diffusivity is extremely strong.Therefore,it can naturally migrate toward a region with relatively negative pressure.In the steep break zone of the MOHO at the 57-65 km depth beneath the earthquake belt,due to mutation of overburden pressure,SCWD can automatically separate out CaSiO3 and other inorganic salts,evolving into the SCW(H2O-CO2-CH4O system.In going upwards to the 10-20-km depth of the crust SCW will be accumulated as an earthquake-pregnant reservoir in the broken terrain.The phase-transition heat of SCW is estimated at 606.62 kJ/kg and the reverse phasing kinetic energy is 2350.8 kJ/kg.When automatic exhaust at the time of decompression reaches the critical pressure(Pc),the instant explosion reverse phase will be normal-state air water.It will release a huge volume of energy and high-kinetic-energy gas which has been expanded by a factor of 1000,leading to the breaking of the country rocks overlying the earthquake-pregnant reservoir,thus giving rise to a Ms 8.0 earthquake.As a result,there were formed eruptive and air-driven(pneumatic) debris flows whose volumatric flow rate reaches n×1014 m3/s,and their force greatly exceeds the power of INT explosive of the same equivalent value.

Calculation of safe drilling mud density window for shale formation by considering chemo-poro-mechanical coupling effect

It is difficult to define safe drilling mud density window for shale sections.To solve this problem,the general Biot effective stress principle developed by Heidug and Wong was modified.The Weibull statistical model was used to characterize the hydration strainrelated strength damage.Considering drilling fluid sealing barrier on shale,a calculation method of safe drilling mud density has been established for shale formation under drilling fluid sealing-inhibition-reverse osmosis effect,combined with a flow-diffusion coupling model.The influence of drilling fluid sealing and inhibiting parameters on safe drilling mud density window was analyzed.The study shows that enhancing drilling fluid sealing performance can reduce the pore pressure transmission and solute diffusion;the inhibiting performance of drilling fluid,especially inhibition to strength damage,is crucial for the wellbore collapse pressure of shale section with significant hydration property.The improvement of drilling fluid sealing and inhibition performance can lower collapse pressure and enhance fracturing pressure,and thus making the safe drilling fluid density window wider and the collapse period of wellbore longer.If there is osmosis flow in shale,induced osmosis flow can make the gap between collapse pressure and fracturing pressure wider,and the stronger the sealing ability of drilling fluid,the wider the gap will be.The safe drilling mud density window calculation method can analyze the relationships between collapse pressure,fracturing pressure and drilling fluid anti collapse performance,and can be used to optimize drilling fluid performance.

一种油基钻开液用延时泥饼解除液体系性能评价

针对常规强酸对油基钻开液泥饼解除不彻底等问题,自研一种温度相应型生酸材料,该材料在常温条件下几乎不反应,当达到储层温度后,会与淡水或盐水反应释放出H+,并以此材料为主剂,优选抑制剂,控制H+在储层下的释放速度,优选表面活性剂及加重材料,形成一种新型油基钻开液用延时泥饼解除液体系,可延时并解除可酸溶固相所形成泥饼,含10%生酸材料解除液体系综合性能评价结果表明:该延时泥饼解除液体系延时作用效果及泥饼解除效果明显,表面活性剂加量可影响该体系泥饼延迟时间及泥饼解除时间,可通过调节不同成分加量对泥饼解除时间进行调控,延时泥饼解除液体系处理后岩心渗透率恢复值可达到90%以上,具有良好的储层保护性能。

高性能密胺降滤失剂的研究

用多聚甲醛与三聚氰胺合成了密胺树脂,对经黏土改性后的丙烯酰胺类聚合物进行包覆,制备了一种抗温抗盐的钻井液降滤失剂。采用单因素实验对样品的加量及耐温耐盐性能进行了评价,实验结果表明,2号样品的性能最佳。在盐浓度为8%的钻井液中,加量为1.5%时,经100℃老化后,2号样品的加量比对照样品减少3%,滤失率为77.7%,性能更优良。