Premium
Integrated geophysical and hydromechanical assessment for CO 2 storage: shallow low permeable reservoir sandstones
Author(s) -
FalconSuarez Ismael,
North Laurence,
Amalokwu Kelvin,
Best Angus
Publication year - 2016
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12396
Subject(s) - geology , brine , permeability (electromagnetism) , electrical resistivity and conductivity , igneous petrology , porosity , saturation (graph theory) , economic geology , pore water pressure , petrology , hydrogeology , petroleum engineering , mineralogy , geotechnical engineering , engineering geology , volcanism , chemistry , metamorphic petrology , biochemistry , mathematics , organic chemistry , combinatorics , membrane , electrical engineering , tectonics , engineering , paleontology
Geological reservoirs can be structurally complex and can respond to CO 2 injection both geochemically and geomechanically. Hence, predicting reservoir formation behaviour in response to CO 2 injection and assessing the resulting hazards are important prerequisites for safe geological CO 2 storage. This requires a detailed study of thermal‐hydro‐mechanical‐chemical coupled phenomena that can be triggered in the reservoir formation, most readily achieved through laboratory simulations of CO 2 injection into typical reservoir formations. Here, we present the first results from a new experimental apparatus of a steady‐state drainage flooding test conducted through a synthetic sandstone sample, simulating real CO 2 storage reservoir conditions in a shallow (∼1 km), low permeability ∼1mD, 26% porosity sandstone formation. The injected pore fluid comprised brine with CO 2 saturation increasing in steps of 20% brine/CO 2 partial flow rates up to 100% CO 2 flow. At each pore fluid stage, an unload/loading cycle of effective pressure was imposed to study the response of the rock under different geomechanical scenarios. The monitoring included axial strains and relative permeability in a continuous mode (hydromechanical assessment), and related geophysical signatures (ultrasonic P‐wave and S‐wave velocities V p and V s , and attenuations Q p −1 and Q s −1 , respectively, and electrical resistivity). On average, the results showed V p and V s dropped ∼7% and ∼4% respectively during the test, whereas Q p −1 increased ∼55% and Q s −1 decreased by ∼25%. From the electrical resistivity data, we estimated a maximum CO 2 saturation of ∼0.5, whereas relative permeability curves were adjusted for both fluids. Comparing the experimental results to theoretical predictions, we found that Gassmann's equations explain V p at high and very low CO 2 saturations, whereas bulk modulus yields results consistent with White and Dutta–Odé model predictions. This is interpreted as a heterogeneous distribution of the two pore fluid phases, corroborated by electrical resistivity tomography images. The integration of laboratory geophysical and hydromechanical observations on representative shallow low‐permeable sandstone reservoir allowed us to distinguish between pure geomechanical responses and those associated with the pore fluid distribution. This is a key aspect in understanding CO 2 injection effects in deep geological reservoirs associated with carbon capture and storage practices.