Micromechanism and mathematical model of stress sensitivity in tight reservoirs of binary granular medium

Research on reservoir rock stress sensitivity has traditionally focused on unary granular structures,neglecting the binary nature of real reservoirs,especially tight reservoirs.Understanding the stresssensitive behavior and mathematical characterization of binary granular media remains a challenging task.In this study,we conducted online-NMR experiments to investigate the permeability and porosity evolution as well as stress-sensitive control mechanisms in tight sandy conglomerate samples.The results revealed stress sensitivity coefficients between 0.042 and 0.098 and permeability damage rates ranging from 65.6%to 90.9%,with an average pore compression coefficient of 0.0168—0.0208 MPa 1.Pore-scale compression occurred in three stages:filling,compression,and compaction,with matrix pores playing a dominant role in pore compression.The stress sensitivity of binary granular media was found to be influenced by the support structure and particle properties.High stress sensitivity was associated with small fine particle size,high fines content,high uniformity coefficient of particle size,high plastic deformation,and low Young's modulus.Matrix-supported samples exhibited a high irreversible permeability damage rate(average=74.2%)and stress sensitivity coefficients(average=0.089),with pore spaces more slit-like.In contrast,grain-supported samples showed low stress sensitivity coefficients(average=0.021)at high stress stages.Based on the experiments,we developed a mathematical model for stress sensitivity in binary granular media,considering binary granular properties and nested interactions using Hertz contact deformation and Poiseuille theory.By describing the change in activity content of fines under stress,we characterized the non-stationary state of compressive deformation in the binary granular structure and classified the reservoir into three categories.The model was applied for production prediction using actual data from the Mahu reservoir in China,showing that the energy retention rates of support-dominated,fill-dominated,and matrix-controlled reservoirs should be higher than 70.1%,88%,and 90.2%,respectively.

Effects of Replacing Fishmeal with Animal By-products Meal Supplementation in Diets on the Growth and Nutrient Utilization of Mangrove Red Snapper

A feeding trial was conducted for 75 d to evaluate the nutritive value of a mixture of animal by-products （MAB） as a possible protein source in diets for juvenile mangrove red snapper, Lutjanus argentimaculatus （mean initial body weight, 30 g）. Fish were fed one of five isonitrogenous diets （40% crude protein） replacing 0, 25% （MAB25）, 50% （MAB50）, 75% （MAB75） and 100% （MAB100） of fish meal protein with similar percentages of MAB. The MAB consisted of 25% cow liver meal, 20% leather meal, 20% meat and bone meal, 15% blood meal, 10% APC （poultry feather meal）, 8% poultry manure dried, 1.5% choline and 0.5% chromic oxide. After 75 d of feeding, fish fed with diets MAB50, MAB75 and MABI00 exhibited significantly lower growth performance than that of fish fed with control and MAB25 diets. The optimum level of MAB was estimated to be 23%. Replacement of fish meal by MAB23% showed the following performance： maximum weight gain, 510%; SGR, 2.39% and FCE, 2.83%. The MAB substitution up to 75% of fish meal protein in diets did not show differences in apparent protein digestibility （83.6% for MAB25, 79.2% for MAB50, 78.7% for MAB75） compared with control （83.4%）, whereas in MABI00 group digestibility （65.3%） was significantly lower than in other groups. The apparent phosphorus absorption of test diet groups was significantly higher （37.1% for MAB25, 28.5% for MABS0, 55.6% for MAB75 and 54.5% for MABI00） than that of control （1 1.2%）. The levels of protein and ash in the whole body, carcass and viscera increased as MAB substitution in diets increased, whereas lipids and moisture remained consistent among all treatment groups. These results showed that approximately 23% of fish meal protein could be replaced by a mixture of animal by-products for juvenile snapper growing from 30 g to 167 g in 75 d without compromising growth performance and feed efficiency.