文档介绍：FINAL REPORT
STRENGTH AND FRACTURE
GRADIENTS
FOR
SHALLOW MARINE SEDIMENTS
Andrew K. Wojtanowicz, Adam T. Bourgoyne, Jr., Desheng Zhou, Kathy Bender
Louisiana State University
Submitted to:
US Department of Interior
Minerals Management Service
381 Elden Street
Herndon, Virginia 20170-4817
Baton Rouge, Louisiana
December 15, 2000
TABLE OF CONTENTS
EXECUTIVE SUMMARY ……………………………………………………………………1
1. BACKGROUND INFORMATION ……………………………………………………….3
Shallow Blowout Statistics ………………………………………………………………3
Significance of Sediment Strength Determination……………………………………..4
2. CHARACTERIZATION OF SHALLOW MARINE SEDIMENTS (SMS)…………….5
Shear Strength of Upper SMS …………………………………………………………..5
Horizontal Stress - Stress Ratio - Elastic Behavior ……………………………………6
Overburden Stress in SMS………………………………………………………………9
Overburden stress as a function of porosity …………………………………………10
New Method for Overburden Stress Estimation in SMS ……………………………11
Density and Shear Strength of SMS from Soil Borings………………………………11
Geotechnical Tests………………………………………………………………………12
Bulk Density and Shear Strength Data ……………………………………………….15
Rock Mechanics Properties of SMS from Soil Borings………………………………17
In situ Stress in SMS………………………..…………………..………………………22
In situ Elastic Stresses …………………………………………………………………22
In situ Plastic Stress Model ……………………………………………………………23
In situ Stresses of SMS in Green Canyon, GOM …………………………………….23
3. SMS FAILURE MECHANISM AROUND OVERPRESSURED BOREHOLES ……..24
Stress Distribution Induced by Drilling - Plastic Zone……………………….………24
Maximum Tangential Stress …………………………………………………..………26
Maximum Vertical Stress ……………………………………………………….……..27
Vertical Fracturing of SMS at Pressurized Wellbore ………………………………29
Vertical Fracture at Elastic Wellbore ………………………………………………..31
Vertical Fracture at Plastic Wellbore ………………………………………………..32
Verification with Finite