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

Integrating Laboratory Testing and Numerical Modelling for a Giant Maturing Carbonate Field in UAE — II. Coupled Geomechanical Modelling of Stacked Reservoir Intervals

2021 ◽  
Author(s):  
Abdelwahab Noufal ◽  
Gaisoni Nasreldin ◽  
Faisal Al-Jenaibi ◽  
Joel Wesley Martin ◽  
Julian Guerra ◽  
...  
Keyword(s):  
Stress State ◽  
Oil And Gas ◽  
Water Injection ◽  
Seismic Inversion ◽  
Second Phase ◽  
High Porosity ◽  
Pore Collapse ◽  
Reservoir Compaction ◽  
Stress Changes ◽  
Field Management

Abstract A mature field located in a gently dipping structure onshore Abu Dhabi has multiple stacked oil and gas reservoirs experiencing different levels of depletion. The average reservoir pressure in some of these intervals had declined from the early production years to the present day by more than 2000 psi. Coupled geomechanical modelling is, therefore, of the greatest value to predict the stress paths in producing reservoir units, using the concept of effective stress. This paper examines the implications for long-term field management—focusing primarily on estimating the potential for reservoir compaction and predicting field subsidence. This paper takes the work reported in Noufal et al. (2020) one step further by integrating the results of a comprehensive geomechanical laboratory characterization study designed to assess the potential geomechanical changes in the stacked reservoirs from pre-production conditions to abandonment. This paper adopts a geomechanical modelling approach integrating a wide array of data—including prestack seismic inversion outputs and dynamic reservoir simulation results. This study comprised four phases. After the completion of rock mechanics testing, the first modelling phase examined geomechanics on a fine scale around individual wells. The goal of the second phase was to build 4D mechanical earth models (4D MEMs) by incorporating 14 reservoir models—resulting in one of the largest 4D MEMs ever built worldwide. The third phase involved determining the present-day stress state—matching calibrated post-production 1D MEMs and interpreted stress features. Lastly, the resulting model was used for field management and formation stimulation applications. The 4D geomechanical modelling results indicated stress changes in the order of several MPa in magnitude compared with the pre-production stress state, and some changes in stress orientations, especially in the vicinity of faults. This was validated using well images and direct stress measurements, indicating the ability of the 4D MEM to capture the changes in stress magnitudes and orientations caused by depletion. In the computed results, the 4D MEM captures the onset of pore collapse and its accelerating response as observed in the laboratory tests conducted on cores taken from different reservoir units. Pore collapse is predicted in later production years in areas with high porosity, and it is localized. The model highlights the influence of stress changes on porosity and permeability changes over time, thus providing insights into the planning of infill drilling and water injection. Qualitatively, the results provide invaluable insights into delineating potential sweet spots for stimulation by hydraulic fracturing.

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.

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
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