Modeling of Reservoir Compaction and Surface Subsidence at South Belridge

1995 ◽  
Vol 10 (03) ◽  
pp. 134-143 ◽  
Author(s):  
K.S. Hansen ◽  
Michael Prats ◽  
C.K. Chan
Keyword(s):  
Surface Subsidence ◽  
Reservoir Compaction

Modeling Thermally Induced Strain in Diatomite

SPE Journal ◽  
2007 ◽  
Vol 12 (01) ◽  
pp. 130-144 ◽  
Author(s):  
James K. Dietrich ◽  
John Donald Scott
Keyword(s):  
Calcium Carbonate ◽  
North Sea ◽  
Effective Stress ◽  
Surface Subsidence ◽  
Thermally Induced ◽  
Silica Phase ◽  
Reservoir Compaction ◽  
The North ◽  
Naturally Occurring ◽  
The North Sea

Summary Diatoms and radiolarians are microorganisms that precipitate Opal-A to form siliceous tests that accumulate on the seafloor to form siliceous oozes. Progressive diagenesis of these deposits during burial results in thick, highly compressible reservoirs of exceptionally high porosity and low permeability, not unlike the chalk reservoirs of the North Sea. During burial and over time, the amorphous silica phase (Opal-A) becomes unstable and gradually changes in its structure to more stable, ordered Opal-A' and crystalline forms or phases of silica, namely Opal-CT and quartz. The Opal-A ? Opal-A' ? Opal-CT ? quartz transformation results in a naturally occurring densification and compaction process that is accelerated by an application of heat. Reservoir compaction and surface subsidence can usually be controlled by injecting fluid to control the effective stress. However, in heavy-oil diatomite reservoirs undergoing steam injection, the injected fluid causes competing effects: it controls effective stress to some degree, yet at the same time it accelerates compaction and subsidence. This paper describes selected results of a diatomite laboratory testing program and features of a unique thermal reservoir simulator formulated to handle the effects on compaction caused by stress, temperature, and time-dependent strain (creep). Elevated temperature in amorphous Opal-A diatomite is shown to be capable of causing a sample compression of 25% or more and a severe reduction in permeability. The effects of thermally induced compaction are expected to accelerate surface subsidence as diatomite steam projects mature. Introduction There is a class of problems involving reservoir compaction of cohesive rocks (e.g. chalk, shale, and diatomite) in which the effects of stress are of a second-order importance compared to those of temperature. The injection of cold seawater in North Sea chalk reservoirs under conditions of invariant effective stress has led to continued compaction and subsidence (Cook et al. 2001; Sylte et al. 1999). The North Sea chalks are nearly pure calcium carbonate, and it is well known that the solubility of calcium carbonate increases as the water temperature decreases. Thus, even under conditions of unchanging effective stress, one would expect gradually increasing dissolution of calcium carbonate and compaction as the reservoir temperature of the chalk (~ 270°F) is gradually lowered by cold seawater injection (Dietrich 2001). In the giant Wilmington field of California, the shaly siltstones that are interbedded with the unconsolidated sands have recently been shown to be much more susceptible to thermally induced compaction than to stress-induced compaction (Dietrich and Norman 2003). And finally, diatomite is known to undergo a silica-phase transformation as temperature is raised, whereby amorphous Opal-A is converted to a more dense, crystalline Opal-CT. The injection of steam into California diatomite reservoirs is expected to accelerate this naturally occurring process and lead to rapid densification and compaction. In each case, for chalk, shaly rocks, and diatomite, there is both a laboratory and field basis that demonstrates the dominant role played by temperature.

Prediction of Abrupt Reservoir Compaction and Surface Subsidence Caused By Pore Collapse in Carbonates

1988 ◽  
Vol 3 (02) ◽  
pp. 340-346 ◽  
Author(s):  
R.M.M. Smits ◽  
J.A. de Waal ◽  
J.F.C. van Kooten
Keyword(s):  
Surface Subsidence ◽  
Pore Collapse ◽  
Reservoir Compaction

Time-dependent Inversion of Surface Subsidence due to Dynamic Reservoir Compaction

2008 ◽  
Vol 40 (2) ◽  
pp. 159-177 ◽  
Author(s):  
A. G. Muntendam-Bos ◽  
I. C. Kroon ◽  
P. A. Fokker
Keyword(s):  
Surface Subsidence ◽  
Time Dependent ◽  
Reservoir Compaction

scholarly journals Subsidence, tremors and society

2001 ◽  
Vol 80 (1) ◽  
pp. 121-136 ◽  
Author(s):  
H.J. Gussinklo ◽  
H.W. Haak ◽  
R.C.H. Quadvlieg ◽  
P.M.F.M. Schutjens ◽  
L. Vogelaar
Keyword(s):  
Monitoring Program ◽  
Gas Production ◽  
Surface Subsidence ◽  
Large Area ◽  
Reservoir Compaction ◽  
Surface Water Management ◽  
Multidisciplinary Study ◽  
Observation Network ◽  
The Sixties ◽  
Set Up

AbstractThe province of Groningen is flat and level, lying at an elevation close to sea level. The area is intensely cultivated and water table levels are a matter of concern. When the size of the Groningen gasfield was recognized in the sixties, it was realized, that substantial subsidence might occur at the surface affecting a large area.Intensive studies were performed over time to predict future subsidence. These studies are supported by theoretical and experimental research in Shell since the 1950’s concerning reservoir compaction and related surface subsidence. To monitor reservoir compaction and surface subsidence on a regular basis, an extensive monitoring program was set up by NAM. The program comprises leveling surveys, GPS measurements, measurements of shallow formation compaction and in-situ reservoir compaction.In Groningen weak earthquakes have occurred since 1991 at irregular intervals. A multidisciplinary study from 1991–1993 on the relationship between gas production and earthquakes in the northern part of the Netherlands, combined with further studies concluded, that under certain circumstances these earthquakes may result from gas production. Monitoring is carried out through a seismic observation network with borehole sensors and locally installed accelerometers.Because of the expected impact of subsidence induced by gas production on surface water management, an Agreement was concluded between the Province of Groningen and NAM.In line with the 1983 Agreement the ‘Commissie Bodemdaling’ was founded, in which both NAM and the Province of Groningen are represented. On the basis of NAM predictions and actual measurements this Committee determines, what measures are to be taken to prevent, minimize or to correct for effects of gas production induced surface subsidence.

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