Surface Gravity Monitoring of the Gas Cap Water Injection Project - Prudhoe Bay, Alaska

Author(s):  
Jerry L. Brady ◽  
John F. Ferguson ◽  
John E. Seibert ◽  
Tianyou Chen ◽  
Jennifer L. Hare ◽  
...  
2002 ◽  
Author(s):  
Jerry L. Brady ◽  
John F. Ferguson ◽  
Carlos V.L. Aiken ◽  
John E. Seibert ◽  
Tianyou Chen ◽  
...  

2004 ◽  
Vol 7 (01) ◽  
pp. 59-67 ◽  
Author(s):  
Jerry L. Brady ◽  
John F. Ferguson ◽  
John E. Seibert ◽  
Tianyou Chen ◽  
Jennifer L. Hare ◽  
...  

2002 ◽  
Author(s):  
Jhaveri Bharat ◽  
Gary Youngren ◽  
Joe Dozzo ◽  
Lynn Schnell ◽  
Matt Maguire

Geophysics ◽  
2008 ◽  
Vol 73 (6) ◽  
pp. WA173-WA180 ◽  
Author(s):  
Jennifer L. Hare ◽  
John F. Ferguson ◽  
Jerry L. Brady

Between March 2003 and March 2007, four high-precision 4D absolute microgravity surveys were performed at Prudhoe Bay, Alaska. These surveys are part of an ongoing effort to monitor the progress of a very large water-injection project in the gas cap of the Prudhoe Bay reservoir at a depth of [Formula: see text]. These carefully acquired gravity data must be modeled and interpreted in terms of water movement within the reservoir. A constrained linear inversion scheme was tested on reservoir simulations during the planning and development phase of this project (preinjection). The inver-sion methodology has been applied to data for three epochs (2005–2003, 2006–2003, and 2007–2003), and mass-distribution models have been produced for the reservoir. The time evolution of the water-mass distribution in the reservoir is visualized from these three snapshot models. The waterflood is expanding into the gas cap at the expected rate but is exhibiting nonsymmetric behavior that is consistent with a greater degree of structural control than expected. The waterflood seems to be restrained episodically and guided by fault barriers. These barriers are overcome and fault-bounded blocks filled with water in stages.


2002 ◽  
Author(s):  
J. M. Brown ◽  
F. J. Klopping ◽  
D. van Westrum ◽  
T. M. Niebauer ◽  
R. Billson ◽  
...  

Geophysics ◽  
1999 ◽  
Vol 64 (1) ◽  
pp. 78-87 ◽  
Author(s):  
Jennifer L. Hare ◽  
John F. Ferguson ◽  
Carlos L. V. Aiken ◽  
Jerry L. Brady

Forward and inverse gravity modeling is carried out on a suite of reservoir simulations of a proposed water injection in the Prudhoe Bay reservoir, Alaska. A novel surveillance technique is developed in which surface gravity observations are used to monitor the progress of a gas cap waterflood in the reservoir at 8200-ft (2500-m) depth. This cost‐effective method requires that high‐precision gravity surveys be repeated over periods of years. Differences in the gravity field with time reflect changes in the reservoir fluid densities. Preliminary field tests at Prudhoe Bay indicates survey accuracy of 5–10 μGal can be achieved for gravity data using a modified Lacoste & Romberg “G” type meter or Scintrex CG-3M combined with the NAVSTAR Global Positioning System (GPS). Forward gravity modeling predicts variations in surface measurements of 100 μGal after 5 years of water injection, and 180–250 μGal after 15 years. We use a constrained least‐squares method to invert synthetic gravity data for subsurface density distributions. The modeling procedure has been formulated and coded to allow testing of the models for sensitivity to gravity sampling patterns, noise types, and various constraints on model parameters such as density, total mass, and moment of inertia. Horizontal‐feature resolution of the waterflood is about 5000 ft (1520 m) for constrained inverse models from synthetic gravity with 5 μGal standard deviation (SD) noise. The inversion method can account for total mass of injected water to within a few percent. Worst‐case scenarios result from inversion of gravity data which are contaminated by high levels (greater than 10–15 μGal SD) of spatially correlated noise, in which case the total mass estimate from inverse models may over or underestimate the mass by 10–20%. The results of the modeling indicate that inversion of time‐lapse gravity data is a viable technique for the monitoring of reservoir gas cap waterfloods.


Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. I33-I43 ◽  
Author(s):  
J. F. Ferguson ◽  
T. Chen ◽  
J. Brady ◽  
C. L. Aiken ◽  
J. Seibert

Between 1994 and 2002, a series of experiments was conducted at Prudhoe Bay, Alaska, aimed at the development of an effective 4D (or time-lapse) gravity technique. Theoretical investigations had pointed out the potential for monitoring water injection in the [Formula: see text]-deep reservoir, but it was not clear that gravity measurements of sufficient accuracy could be made in the arctic environment. During the course of these experiments, new techniques and instrumentation were introduced and perfected for both gravity and position measurements. Gravity stations are located using high-precision global positioning system (GPS) techniques without permanent monuments. Robust methods for meter drift control have improved noise resistance in relative gravimeter surveys. Absolute gravity measurements with a field-portable instrument maintain absolute gravity levels among surveys. A 4D gravity-difference noise of [Formula: see text] standard deviation has been established at Prudhoe Bay for GPS-controlled relative gravimeter surveys. The lessons learned are now being applied to full-scale waterflood monitoring at Prudhoe Bay. The basic technique is applicable to microgravity surveys and 4D microgravity surveys for any purpose.


Author(s):  
Hyun Sun Park ◽  
Norihiro Yamano ◽  
Kiyofumi Moriyama ◽  
Yu Maruyama ◽  
Yanhua Yang ◽  
...  

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