Absolute porosity and pore size determination of pore types in media with varying pore sizes
AssigneeSaudi Arabian Oil Company
InventorsHYUNG T. KWAK, Ali A. Al-Yousif, Salah H. Al-Saleh
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Abstract
The longitudinal relaxation times (T1) of water and hydrocarbon inside porous media, such as rock from subsurface formations, behave differently when external magnetic fields vary. A Nuclear Magnetic Relaxation Dispersion (NMRD) profile from Fast Field Cycling Nuclear Magnetic Resonance (FFC-NMR) technique differentiates the type of fluids filling the pores. Different types of pores in a rock sample are filled with different fluids, water and hydrocarbon, and the absolute porosity and the pore size of each type of pores is determined.
Claims3
A method of obtaining a measure of porosity and pore size in the rock sample from a subsurface hydrocarbon reservoir from nuclear magnetic resonance dispersion profiles of the rock sample and nuclear magnetic resonance relaxation times, comprising the steps of:
- treating the rock sample with paramagnetic ions to coat pores on the rock sample to produce the nuclear magnetic resonance dispersion profiles;
- obtaining nuclear magnetic resonance relaxation times of the rock sample fully saturated with water;
- obtaining a nuclear magnetic resonance dispersion profile of the rock sample at irreducible water saturation;
- identifying pore types in the pores of the rock sample based on the obtained nuclear magnetic resonance dispersion profile of the rock sample at irreducible water saturation;
- determining porosity of the identified pore types based on the nuclear magnetic resonance relaxation times;
- and
- determining pore size of the identified pore types based on the nuclear magnetic resonance relaxation times.
A method of obtaining a measure of absolute porosity and pore size of pore types in a rock sample from nuclear magnetic resonance dispersion profiles of the rock sample and nuclear magnetic resonance relaxation times, comprising the steps of:
- treating the rock sample with paramagnetic ions to coat pores on the rock sample to produce the nuclear magnetic resonance dispersion profiles;
- obtaining nuclear magnetic resonance relaxation times of the rock sample fully saturated with water;
- obtaining a nuclear magnetic resonance dispersion profile of the rock sample at irreducible water saturation;
- identifying pore types in the pores of the rock sample based on the obtained nuclear magnetic resonance dispersion profile of the rock sample at irreducible water saturation;
- determining absolute porosity of the identified pore types based on the nuclear magnetic resonance relaxation times;
- and
- determining pore size of the identified pore types based on the nuclear magnetic resonance relaxation times.
A method of obtaining a measure of porosity and pore size in the rock sample from a subsurface hydrocarbon reservoir, comprising the steps of:
- obtaining nuclear magnetic resonance relaxation times of the rock sample fully saturated with water;
- conducting forced drainage of the rock sample by fully saturating the rock sample with hydrocarbon liquid to obtain irreducible water saturation of the rock sample;
- obtaining a nuclear magnetic resonance dispersion profile of the rock sample at irreducible water saturation;
- identifying pore types in the pores of the rock sample based on the obtained nuclear magnetic resonance dispersion profile of the rock sample at irreducible water saturation;
- determining porosity of the identified pore types based on the nuclear magnetic resonance relaxation times;
- and
- determining pore size of the identified pore types based on the nuclear magnetic resonance relaxation times.
Dependencies are inferred from the claim text.