Spatial variations of pore pressure
Disclosed are methods, systems, and computer-readable medium to perform operations for calculating pore pressure in a reservoir, the operations including: receiving input data including: (i) a rock density in the reservoir, (ii) seismic data measured in the reservoir, and (iii) pore pressure measurement data from a Modular Formation Dynamic Tester (MDT); calculating, based on the rock density, an overburden pressure volume of the reservoir; generating, based on the overburden pressure volume, an overburden pressure volume of the reservoir; generating, based on the seismic data, an acoustic impedance volume of the reservoir; generating, based on the effective stress and overburden volumes, an estimated pore pressure volume of the reservoir; and calculating, based on the estimated pore pressure volume, a pore pressure gradient map indicative of the pore pressure in the reservoir.
1 . A method for calculating pore pressure in a reservoir, the method comprising:
receiving input data comprising: (i) a rock density in the reservoir, (ii) seismic data measured in the reservoir, and (iii) pore pressure measurement data from a Modular Formation Dynamic Tester (MDT);
calculating, based on the rock density, an overburden pressure volume of the reservoir;
generating, based on the seismic data, an acoustic impedance volume of the reservoir;
calculating, based on the overburden pressure volume and the pore pressure measurement data, an effective stress volume of the reservoir;
generating, based on the effective stress volume and the overburden pressure volume, an estimated pore pressure volume of the reservoir;
selecting a first top reservoir surface on a first depth seismic volume;
flattening the first depth seismic volume based on a reference top reservoir surface by correcting effects of structural variation in the subsurface beneath the first top reservoir surface aligning with the reference top reservoir surface for unifying top reservoir surfaces into the reference top reservoir surface;
calculating a first estimated pore pressure volume based on the reference top reservoir surface;
selecting a second top reservoir surface on a second depth seismic volume;
flattening the second depth seismic volume and obtain a second estimated pore pressure volume based on the reference top reservoir surface;
calculating a pore pressure gradient map, by dividing the pore pressure values on the flattened reservoir surface by an average reservoir depth; and
generating instructions for a drilling system to perform a drilling operation determined by one or more actions comprising a determination of a drill location based on the pore pressure gradient map and anticipated drilling hazards.
2 . The method of claim 1 , wherein calculating, based on the rock density, the overburden pressure volume of the reservoir comprises:
calculating an overburden pressure dataset as
P
overburden
=
∫
surface
depth
p
(
z
)
g
dz
,
where p(z) is the rock density of the rock above a depth z, and g is a gravity acceleration in meter/second 2 (m/s 2 ); and
generating the overburden pressure volume based on the overburden pressure dataset.
3 . The method of claim 2 , wherein the overburden pressure dataset is calculated at one or more potential well locations.
4 . The method of claim 2 , wherein the overburden pressure volume is generated based on the overburden pressure dataset using a Sequential Gaussian distribution method.
5 . The method of claim 1 , wherein generating, based on the seismic data, the acoustic impedance volume of the reservoir comprises using seismic inversion to transform the seismic data into the acoustic impedance volume.
6 . The method of claim 1 , wherein calculating, based on the overburden pressure volume and the pore pressure measurements, the effective stress volume of the reservoir comprises subtracting the pore pressure measurements from the overburden pressure volume.
7 . The method of claim 1 , wherein generating, based on the effective stress volume and the overburden volume, the estimated pore pressure volume of the reservoir comprises subtracting the effective stress volume from the overburden volume.
8 . The method of claim 1 , wherein the drilling operation comprises: delivering a proper mud weight for the drilling operation to avoid formation collapse, well kicks, blowouts, or stuck pipe scenarios.
9 . A system for calculating pore pressure in a reservoir, the system comprising:
one or more processors configured to perform operations comprising:
receiving input data comprising: (i) a rock density in the reservoir, (ii) seismic data measured in the reservoir, and (iii) pore pressure measurement data from a Modular Formation Dynamic Tester (MDT);
calculating, based on the rock density, an overburden pressure volume of the reservoir;
generating, based on the seismic data, an acoustic impedance volume of the reservoir;
calculating, based on the overburden pressure volume and the pore pressure measurement data, an effective stress volume of the reservoir;
generating, based on the effective stress volume and the overburden pressure volume, an estimated pore pressure volume of the reservoir;
selecting a first top reservoir surface on a first depth seismic volume;
flattening the first depth seismic volume based on a reference top reservoir surface by correcting effects of structural variation in the subsurface beneath the first top reservoir surface aligning with the reference top reservoir surface for unifying top reservoir surfaces into the reference top reservoir surface;
calculating a first estimated pore pressure volume based on the reference top reservoir surface;
selecting a second top reservoir surface on a second depth seismic volume;
flattening the second depth seismic volume and obtain a second estimated pore pressure volume based on the reference top reservoir surface;
calculating a pore pressure gradient map, by dividing the pore pressure values on the flattened reservoir surface by an average reservoir depth; and
generating instructions for a drilling system to perform a drilling operation determined by one or more actions comprising a determination of a drill location based on the pore pressure gradient map and anticipated drilling hazards.
10 . The system of claim 9 , wherein calculating, based on the rock density, the overburden pressure volume of the reservoir comprises:
calculating an overburden pressure dataset as
P
overburden
=
∫
surface
depth
p
(
z
)
g
dz
,
where p(z) is the rock density of the rock above a depth z, and g is a gravity acceleration in meter/second 2 (m/s 2 ); and
generating the overburden pressure volume based on the overburden pressure dataset.
11 . The system of claim 10 , wherein the overburden pressure dataset is calculated at one or more potential well locations.
12 . The system of claim 10 , wherein the overburden pressure volume is generated based on the overburden pressure dataset using a Sequential Gaussian distribution method.
13 . The system of claim 9 , wherein generating, based on the seismic data, the acoustic impedance volume of the reservoir comprises using seismic inversion to transform the seismic data into the acoustic impedance volume.
14 . The system of claim 9 , wherein calculating, based on the overburden pressure volume and the pore pressure measurements, the effective stress volume of the reservoir comprises subtracting the pore pressure measurements from the overburden pressure volume.
15 . The system of claim 9 , wherein generating, based on the effective stress volume and the overburden volume, the estimated pore pressure volume of the reservoir comprises subtracting the effective stress volume from the overburden volume.
16 . The system of claim 9 , wherein the drilling operation comprises: delivering a proper mud weight for the drilling operation to avoid formation collapse, well kicks, blowouts, or stuck pipe scenarios.
17 . A non-transitory computer storage medium encoded with instructions that, when executed by one or more computers, cause the one or more computers to perform operations for calculating pore pressure in a reservoir, the operations comprising:
receiving input data comprising: (i) a rock density in the reservoir, (ii) seismic data measured in the reservoir, and (iii) pore pressure measurement data from a Modular Formation Dynamic Tester (MDT);
calculating, based on the rock density, an overburden pressure volume of the reservoir;
generating, based on the seismic data, an acoustic impedance volume of the reservoir;
calculating, based on the overburden pressure volume and the pore pressure measurement data, an effective stress volume of the reservoir;
generating, based on the effective stress volume and the overburden pressure volume, an estimated pore pressure volume of the reservoir;
selecting a first top reservoir surface on a first depth seismic volume;
flattening the first depth seismic volume based on a reference top reservoir surface by correcting effects of structural variation in the subsurface beneath the first top reservoir surface aligning with the reference top reservoir surface for unifying top reservoir surfaces into the reference top reservoir surface;
calculating a first estimated pore pressure volume based on the reference top reservoir surface;
selecting a second top reservoir surface on a second depth seismic volume;
flattening the second depth seismic volume and obtain a second estimated pore pressure volume based on the reference top reservoir surface;
calculating a pore pressure gradient map, by dividing the pore pressure values on the flattened reservoir surface by an average reservoir depth; and
generating instructions for a drilling system to perform a drilling operation determined by one or more actions comprising a determination of a drill location based on the pore pressure gradient map and anticipated drilling hazards.
18 . The non-transitory computer storage medium of claim 17 , wherein calculating, based on the rock density, the overburden pressure volume of the reservoir comprises:
calculating an overburden pressure dataset as
P
overburden
=
∫
surface
depth
p
(
z
)
g
dz
,
where p(z) is the rock density of the rock above a depth z, and g is a gravity acceleration in meter/second 2 (m/s 2 ); and
generating the overburden pressure volume based on the overburden pressure dataset.
19 . The non-transitory computer storage medium of claim 18 , wherein the overburden pressure dataset is calculated at one or more potential well locations.
20 . The non-transitory computer storage medium of claim 18 , wherein the overburden pressure volume is generated based on the overburden pressure dataset using a Sequential Gaussian distribution method.