Cause Of Compaction Research Articles

Formation damage of sandstone geothermal reservoirs: During decreased salinity water injection

Water reinjection was widely implemented in the geothermal development for not only disposing tailwater but also maintaining reservoir pressure. Accompanying this was the formation damage, especially in the injection of decreased salinity water which was synthesized by adding surface water and condensed water into produced water for inhibiting the process equipment corrosion, treating the cooling tower condensate, and etc. Fine migration is the prevailing mechanism; however, it is insufficient in some scenarios. Multiple experiments were conducted to investigate the characteristics and mechanisms of formation damage of sandstone geothermal reservoirs during the decreased salinity water injection. First, coreflooding (CF), nuclear magnetic resonance (NMR), and contact angle (CA) experiments were conducted to analyze the characteristics of the formation damage. Subsequently, scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and nanoindentation experiments were implemented to study the corresponding mechanisms. Finally, the damage mode of sandstone geothermal reservoirs in decreased salinity water injection was proposed. The CF, NMR, and CA experimental results indicated that the decreased salinity water injection resulted in severe formation damage, as manifested by the reduction of permeability, shrinkage of the pore-throat, and enhancement of the water-wettability of core samples. That is, formation damage not only indicates that the fluid is more difficult to be injected but also that it is more difficult for the injected fluid to flow. As the salinity decreases, these trends gradually enhance. The SEM results illustrated that fine migration is noticeable in decreased salinity water injection, meanwhile mineral dissolution which causes secondary pores and microfracture is also apparent. Both reactions are enhanced as the salinity decreases. The same conclusion was validated by the XRD and ICP-OES results, as manifested by the decrease in the concentrations of clay, K-feldspar, and plagioclase, and the increase in quartz, as well as the emergence of Si4+, Mg2+, Ca2+, and K+ in the effluents produced during the decreased salinity water injection. The nanoindentation results explicated that mineral dissolution weakened the mechanical strength of the minerals, which might effectively facilitate compaction. The elastic modulus and hardness of the quartz, K-feldspar, and plagioclase decreased from 107.5&93.7&72.3GPa and 13.7&10.1&7.4GPa of the original sandstone to 108.1&86.0&69.5GPa and 13.6&10.3&6.4GPa of the deionized water flushed one, respectively. In conclusion, formation damage was synergistically dominated by the external cause of compaction and the internal causes of fine migration and mineral dissolution. These factors compressed the pore-throat, decreased the connectivity of the porous media, enhanced the water-wettability of the sandstone surface, and consequently impeded water flow.

Research of the reasons of excessing the air and underground soil layers of the deep blocked soils of black earth

Purpose. Investigation of the causes of compaction of arable and subsoil soil layers of deep podzolic chernozems. Methods. Experimental studies of the density of arable and subsoil soil layers of deep podzolic chernozems with subsequent processing of the results on a PC. Results. The results of experimental researches of formation of the overcompacted layers of chernozems of deep podzolic depending on ways and means of influence on them are stated. Conclusions. As a result of research it is established that on deep chernozem chernozems the maximum depth of overcompacted layers formed by self-compaction for virgin soil does not exceed 30 cm, and man-made impact on these soils leads to overcompaction of layers up to 40 cm deep. Possible areas of further research on this issue are the study of technical and technological aspects of ensuring acceptable for optimal plant development density. Keywords: overcompaction, arable and subsoil layers of soil, division of chernozems deep podzolic, running systems, soil density.

PHYSICAL QUALITY OF SOIL IN MECHANIZED THINNING OF Eucalyptus sp.

The traffic of machines is the main cause of compaction of forest soils, causing soil deformations, due to the pressures exerted by the machines, both at the time of cutting and in the transshipment of wood. In this sense, this work had as objective to evaluate soil compaction, caused by the traffic of machines, in the mechanized thinning operation of Eucalyptus saligna Smith. This study was carried out in forest stands, in the municipality of Butiá, RS. Changes in soil physical properties were evaluated in three treatments: with no traffic; after cutting; and after wood transshipment. The forest inventory and collection of undisturbed soil samples were carried out to determine microporosity, macroporosity and bulk density. The experimental design was the completely randomized, in a bifactorial arrangement, with subdivided plots. For the comparison of the physical attributes, the Tukey test (p≤0.05) of significance was used. The results evidenced increase in soil density values, mainly in the treatment after transshipment and decrease in macropores, with values close to and below the limit considerable as detrimental to the development of the plants. The knowledge of soil deformations caused by forest operations contributes to the improvement of future processes aiming to guide the physical quality of the soil, in order to offer beneficial conditions to the growth of the plants.

Soil compaction effects on soil health and cropproductivity: an overview.

Soil compaction causes substantial reduction in agriculture productivity and has always been of great distress for farmers. Intensive agriculture seems to be more crucial in causing compaction. High mechanical load, less crop diversification, intensive grazing, and irrigation methods lead to soil compaction. It is further exasperated when these factors are accompanied with low organic matter, animal trampling, engine vibrations, and tillage at high moisture contents. Soil compaction increases soil bulk density and soil strength, while decreases porosity, aggregate stability index, soil hydraulic conductivity, and nutrient availability, thus reduces soil health. Consequently, it lowers crop performance via stunted aboveground growth coupled with reduced root growth. This paper reviews the potential causes of compaction and its consequences that have been published in last two decades. Various morphological and physiological alterations in plant as result of soil compaction have also been discussed in this review.

Comparison of methods for estimating the carcass stiffness of agricultural tyres on hard surfaces

Loading soil via pneumatic tyres is a major cause of compaction of agricultural soils, which causes damage to the soil-water-air-plant system. The loads applied to the soil and the resulting pressure influences the degree of soil compaction. This study was conducted to determine an effective method to measure the pressure distribution under a selection of pneumatic agricultural tyres. This was conducted initially on a non-deformable surface; a later study will consider pressures within the subsoil. From this the tyre carcass stiffness was determined and methods to predict carcass stiffness were evaluated. Tyre carcass stiffness is defined as an equivalent pressure resulting from the stiffness of the tyre carcass. In order to estimate the carcass stiffness of tyres a number of approaches were considered including: (i) footprint area, (ii) tyre load – deflection, (iii) pressure mapping and (iv) tyre manufacturer's specification methods. Carcass stiffness values obtained from the footprint area method gave results significantly lower (30–40%) than those obtained using the pressure mapping system. The method based on the tyre load – deflection characteristics was found to give a better estimation of the tyre carcass stiffness of the smooth rather than the treaded tyre. The technique of using the tyre manufacturer's specification data, where the estimation of the tyre carcass stiffness was calculated using the theoretical load that the tyre could support at zero inflation pressure, produced estimates that were within ±20% of the mean carcass stiffness determined using the pressure mapping system.