Experimental Study on Seepage Characteristics of a Soil-Rock Mixture in a Fault Zone

Abstract

A mixture of fault gouge and rubble taken out from a fault zone is used to prepare a S-RM (Soil-Rock Mixture) sample with rock block proportions of 20%, 30%, 40%, 50%, 60% and 70%, respectively. A GDS triaxial test system is used accordingly to measure the seepage characteristics of such samples under different loading and unloading confining pressures in order to determine the variation law of the permeability coefficient. The test results show that: (1) The permeability coefficient of the S-RM samples decreases as the pressure increases, and the decrease rate of this coefficient in the initial stage of confining pressure loading is obviously higher than in the semi-late period; (2) The permeability coefficient at different confining pressure levels presents a common trend as the rock block proportion is increased, i.e., it decreases first then it increases (the permeability coefficient of the sample with rock block proportion 40% being the smallest, 70% the largest); (3) In the stage of confining pressure unloading, the recovery degree of the permeability coefficient grows with the increase of rock block proportion (the recovery rate of S-RM sample with rock block proportion 70% reaches 50.2%); (4) In the stage of confining pressure loading and unloading, the sensitivity of the permeability coefficient to the rock block proportion displays the inverse "Z" variation rule (when rock block proportion reaches 60%, the sensitivity is highest);(5) In the stage of confining pressure loading, the relationship between the permeability coefficient and confining pressure can be described by an exponential relationship.

Analysis of the Applicability of a Risk Quantitative Evaluation Method to High Temperature-Pressure Drilling Engineering

“…Through the statistical analysis of logging data, core laboratory experimental data and LOT data, the structural stress coefficients of each well are obtained, and then these coefficients are counted to obtain range and distribution of their values; 4. Calculated rock mechanical parameters and tectonic stress coefficient are substituted into the calculation formula of formation collapse and fracture pressure [17], and formation collapse and fracture pressures are calculated to obtain formation collapse pressure and fracture pressure profile with probability information; 5. Finally, according to practical drilling fluid density and formation pressure measured data of adjacent wells, four formation pressure profiles with credibility are corrected by translation or interpolation; 6.…”

Analysis of Channeling-Path Phenomena in a Complex Fault-Block Reservoir with Low Recovery Factor and High Water-Cut Ratio

“…Fault block M is a typical "three highs and two lows" complex fault-block reservoir in the NB study area, with an oil-bearing area of 0.94 km 2 . It was put into production in 2008, with depletion production in the early stages, and water injection began in 2011.…”

“…The so-called "three highs and two lows" refer to high comprehensive water cut (average, 86.2%), high operating cost (average, 1072 yuan/ton), high natural decline rate (average, 20%/year), low oil recovery rate from geological reserves (average, 0.58%/year), and low recovery degree of geological reserves (average, 14.5%). How to effectively identify channeling channels in such reservoirs is of great practical significance in terms of improving the development effect of the reservoirs, prolonging the development life of the reservoirs, rationally formulating the development adjustment measures, and improving the ultimate oil recovery of the reservoirs [1][2][3].…”

Effect of Dry-Wet Cycles on the Transport and Mechanical Properties of Cement Mortar Subjected to Sulfate Attack

“…Ye et al [42] have also confirmed this finding. The permeability decreases significantly as the confining pressure increases because the internal pore structure and penetrating fractures are compressed under the confining pressure, reducing the free path for the gas and thus reducing the gas flow [46].…”