Geophysical Reservoir Monitoring GRM systems such 4D seismic are increasingly used in the oil and gas industry because they provide unique and useful information on fluid movement within the reservoir. This information is relevant for many reservoir management decisions; including new well placement, well intervention, and reservoir model updating.
Unfortunately, it has been difficult to estimate the value creation of any data acquisition scheme due to the fact that a multidisciplinary approach is required to model the value that future measurements will imply in future decisions. This assessment requires a common decision making simulation frame work that can integrate the input from geo-modelers, geophysicist and reservoir engineers.
This work presents an example of how a Close Loop Reservoir Management (CLRM) simplification can be used as a framework for simulating NPV changes due to assimilation of production and saturations in a simple toy model. It combines state-of-the-art data assimilation and uncertainty modeling methods with a robust optimization genetic algorithm to calculate NPV improvements due to model update and its relationship with the NPV obtained from the synthetic reservoir.
In this context a simple synthetic model is presented. It recreates a segment of green field under a strong aquifer influence with two discovery wells. The reservoir development requires the selection of 4 well locations at fixed drilling times. The development strategy selection is obtained with the use of a genetic algorithm within the CLRM framework. Subsequently two cases are presented: one of assimilating only production after the first two wells have been drilled, just before deciding the locations of the last two wells; and a second case, in which production and saturation are assimilated at the same time. The saturation map assimilated is assumed to be output of a 4D seismic acquisition. The model update imposes the need of optimally relocate the last two wells which results in a NPV change.
The results show how the obtained NPVs is incremented by the relocation of the last two wells in both cases. A bigger increment is obtained when both, production and saturation are assimilated. In addition, the ensemble improved its forecast capability the most, when saturation assimilation is included. Nevertheless, the ensemble expected NPV decreases after assimilation from the value obtained from the first development strategy optimization; this indicates an optimistic early NPV valuation due to the initial ensemble distributions spread.
The study presents an asset simulation framework that could be used to evaluate data acquisition investments through the systematic modeling of reservoir uncertainties with in a decision oriented focus. This could include the inclusion of additional uncertain model parameters, the insertion of water injector and well conversions, the assimilation of saturations at different intervals, the change on the quality of the saturation maps assimilated, in addition to sensitivity studies of other economic constrains.
Surface seismic technology offers a promising technique for monitoring carbon dioxide (CO2) flood fronts during the enhanced-oil-recovery (EOR) process. Changes in the seismic signature have been observed with CO2 flooding, but its quantification with respect to subsurface saturation is still in its infancy. This study is focused on quantifying variation in the seismic parameters (velocity and impedance) as a function of subsurface fluid type and saturation.
We present results of a laboratory study in which velocity and density were monitored as the pore fluids (formation brine and oil, and CO2) were replaced sequentially. All the experiments were performed at in-situ pressure conditions on core plugs (Tuscaloosa Sandstone) recovered from a well in a field currently undergoing CO2 flooding. These plugs are characterized as fluvial (quartz ˜87%, clay ˜10%) and distributary channels (quartz ≈75%, clay ≈17%).
When dry samples were flooded with brine, a decrease in compressional-wave (P-wave) velocity (≈2%) was observed until 95% saturation of brine was achieved. For the remaining 5% of saturation, the velocity increased by 7 to 12.5%. After attaining 100% brine saturation, oil was pumped to displace the brine until irreducible water saturation was achieved. A linear drop of 3 to 4% in velocity to oil saturation was observed during this step. Thereafter, liquid CO2 was injected to displace the oil/brine system and a drop of 5 to 10% in P-wave velocity was observed. Biot-Gassmann modeling shows good agreement with experimental results for the gas/brine and oil/brine systems, but not for liquid-CO2 flooding.
An empirical relationship was derived from the experimental results, and was applied to sonic logs and used for sensitivity analysis of 4D-seismic data. Post-flooded sonic data were compared to a theoretical sonic curve estimated from an empirical and ‘patchy’ model. Also, a significant increase in seismic amplitude difference was observed when CO2 saturation was greater than 50%.
Summary A new stochastic inversion algorithm is developed incorporating a method of computer vision, known as image quilting. The main stochastic inversion is implemented in a multiple point statistics manner, incorporating training image. The image quilting algorithm helps us to modify the number of random location visitis, and the multiple point statistics algorithm provides a more detailed definition for the litho-facies in the reservoir. Introduction Considering the depositional and geological complexity of the fluvial deltaic systems, such as Delhi Field, application of conventional geostatistics for reservoir modeling or conventional seismic inversion approaches will not obtain an accurate litho-facies and rock property model for the field. Therefore, incorporation of advanced geostatistical approaches that can capture the complex depositional features of the reservoir is of great importance.
Al-Mudhafar, Watheq J. (Louisiana State University) | Al-Tameemi, Abdullah (Louisiana State University) | Al-Maliki, Ali K. (Basra Oil Company) | Al-Attar, Atheer (Weatherford International) | Al-Ameri, Riyam H. (Basra Oil Company)
The Gas-Assisted Gravity Drainage (GAGD) process has been suggested to improve oil recovery in both secondary and tertiary recovery through immiscible and miscible injection modes. In contrast of Continuous Gas Injection (CGI) and Water-Alternative Gas (WAG), the GAGD process takes advantage of the natural segregation of reservoir fluids to provide gravity-stable oil displacement and improve oil recovery. In the GAGD process, the gas is injected through vertical wells to formulate a gas cap to allow oil and water drain down to the horizontal producer (s). The GAGD process has been invented based on experimental work at Louisiana State University. Limited studies have been conducted to test its effectiveness in real oil field evaluations.
In this paper, a comprehensive literature review was presented to summarize all the references about the GAGD process concepts, principles, and field-scale evaluations. Particularly, the paper presents introduction about the mechanisms of cO2-rock-fluid interactions, gas injection approaches for Enhanced Oil recovery, the physical model description and evaluation of the GAGD process physical Model, the factors influencing the GAGD process, and finally a review of all the previous field-scale evaluation studies. Moreover, the validation of the GAGD process in field-scale application was fully discussed by focusing the light on its weak points with respect to the optimal implementation design for achieving maximum oil recovery.
The paper ended with field-scale compositional simulations of the GAGD process in the 5th SPE comparative solution project model and the heterogeneous upper sandstone oil reservoir in the South Rumaila oil field, located in Southern Iraq. Four gas mixtures were injected: CO2, Flue Gas, Nitrogen to Methane, and associated gas production (AGP). It can be concluded that the immiscible flooding of the AGP-AGD in the South Rumaila field has the same effect of using the CO2 with respect to attaining a promising oil recovery. Consequently, AGP can be efficiently utilized for an EOR project in the Rumaila field as an alternative to the carbon dioxide.
L'ut, e mechanism of oil production is inherently one of a continual change in 14.e volumetric contents of the oil-producing section. Of necessity, the od expelled must be displaced either by gas or by water.' Accordingly, as production proceeds, the average oil saturation in the original reservoir Mo notonically decreases--except when the production is the result of rese ll rvoir liquid expansion--while the resultant saturation of the displacing ase.of gas or water, or both, simultaneously increases. Nevertheless oLnere is value in a consideration of the theoretical steady-state behavior f m ultiphase-fluid systems, for two reasons. The first is that, as pointed out in the preceding chapter, a rigorous analysis of time-varying systems by means of Eqs. This un-rtunate circumstance in itself does not, of course, make the steady-state lanalcgue of a particular transient system a practical equivalent of the atter. On the other hand, such steady-state analogues will provide a'de to the qualitative interpretation and understanding of the behavior:L.
Permanent borehole sensors provide a means of acquiring repeated time-lapse 3D VSP seismic surveys to image the subsurface geology and monitor CO2 injection for a tertiary enhanced oil recovery (EOR) project at Hastings Field, Texas. Five time-lapse episodes have been acquired, processed and evaluated over a 29-month time period. The results show a high-resolution 3D image of the faulted target reservoir while dynamically providing snapshots of the CO2 injection throughout the injection process.
Presentation Date: Tuesday, October 18, 2016
Start Time: 11:10:00 AM
Presentation Type: ORAL
We introduce the Depth to Surface Resistivity (DSR) method as a tool that can be used to assist in detection and monitoring of CO2 and water floods within a reservoir. DSR injects current directly into the formation by energizing the metallic well casing itself, either at depth or at the surface of the well, and the resulting electric fields are measured by capacitive electrodes at the surface of the earth. The resulting potential differences are inverted to generate a resistivity model, which can be interpreted to give information about the location of injected fluids. We demonstrate the effectiveness of the DSR method with a synthetic example based on results from a field study in Texas for a CO2 flood.
Presentation Date: Wednesday, October 19, 2016
Start Time: 2:20:00 PM
Presentation Type: ORAL
The focus of this study is on shear wave splitting caused by preferential fractures and differential stress. Multicomponentmultisource offshore seismic data events recorded by arrays of three-component (3C) digital seismometers of Malay Basin provides valuable insight into the use of shear-wave splitting (SWS) measurements. The properties of shear wave splitting can be used to infer (1) the directional dependence of polarization (ϕ) in fractures medium, usually parallel to crack orientation; and (2) the measurement of delay time (δt) between the two split S-waves is proponational to the number of cracks per unit volume with splitting uncertainties.
Seismic anisotropy (i.e. the dependence of seismic velocities on the direction of propagation) due to fractures causes great interests in modern seismic exploration. When a shear wave propagrates through an anisotropic or fractured media, unlike compressional (P) waves, shear waves are characterized by having different polarization into fast and slow shear waves. Shear waves propagating in anisotropic medium are called inline (SV) and cross-line (SH) (Crampin, 1981; Alford, 1986). The SV-wave is polarized in the plane of propagation, while the SH-wave is polarized orthogonal to the plane of the propagation. However, in layered medium, the SV-wave is polarized in the radial direction, and SH-wave would be in the transverse direction. In isotropic medium, we would expect radial component but not the transverse component (Figure 1a), because it is dominated by SV-wave energy from P-SV conversion. On the other hand in the presence of azimuthal anisotropy, the polarization are determined by the natural axes of the anisotropic medium (Figure 1b) and shear wave energy is subjected to polarization during splitting (Alford, 1986).
Figure 1: Polarization of shear wave propogation. In case of isotropic (a), the polarization is depends on source-receiver configuration. For anisotropic case (b), it is determined by anisotropic fracture orientation (Figure modified from (Bale et al., 2009)
Al Eidan, A. A. (Saudi Aramco PE&D) | Bachu, S. (Alberta Innovates Technology Futures) | Melzer, L. S. (Melzer Exploration Co.) | Lars, E. I. (CLIMIT Programme, Resarch Council) | Ackiewicz, M. (US Department of Energy)
While enhanced oil recovery using carbon dioxide (CO2-EOR) is a mature technology and known to concurrently store large volumes of CO2, it is not currently viewed by industry as a CO2 storage process. Application of CO2-EOR for CO2 storage to reduce anthropogenic CO2 emissions 1) enables carbon capture and storage (CCS) technology improvement and cost reduction; 2) improves the business case for CCS demonstration and early movers; 3) supports the development of CO2 transportation networks; 4) may provide significant CO2 storage capacity in the short-to-medium-term, particularly if residual oil zones (ROZ) are produced and hybrid CO2-EOR/CCS operations are considered; 5) enables knowledge transfer; and 6) it helps gaining public and policy-makers acceptance. Although there are a number of commonalities between CO2-EOR and pure CO2 storage operations, currently there are a significant number of differences between the two types of operations that can be grouped in five broad categories: 1) operational; 2) objectives and economics, including CO2 supply, demand and purity; 3) legal and regulatory; 4) long term CO2 monitoring requirements; and 5) industry's experience. There are no specific technological barriers or challenges
OSV (On-Site Visualization) is a monitoring system in which measured information is shared visually on a real time basis at site. It was introduced by Akutagawa in 2006 and it has been applied at various construction sites in Japan and overseas projects.
Through OSV application on various overseas projects, it has been recognized that a major problem with OSV system is the high cost of electrically driven OSV devices needed to cover many locations for a more effective OSV operation.
Based on the above observation, low cost OSV were developed and trial installation was conducted at the slope of National Highway in Vietnam.
Hanoi Metro Line 2 has been implemented since Mar 2011 under Japanese ODA and the construction works start in 2015. Because the underground station has deep open excavation works located at downtown in Hanoi, the careful construction operation with instrumentation and monitoring are required. In this paper, the plan of various type of OSV installation on Hanoi Metro Line 2 is proposed and the effectiveness of OSV monitoring is examined.
Recently the installation of safety monitoring systems at construction sites has become mandatory and everyone recognizes the importance and requirement of safety. However the ratio of injuries and fatalities have not been reduced so much in Japan1 as well as other countries2.A new approach for the safety monitoring of infrastructure and visually sharing the measured information on a real time basis was proposed by Akutagawa in 2006 and has been implemented in more than 50 construction sites including overseas projects in New Delhi and Bangalore3) - 6) to improve safety management practices. This new approach is derived by utilizing an On-Site Visualization system, whereby light emitting sensors are used as the key technology for monitoring and giving simultaneous visual presentation of the measured information of structure and ground movement information on site. Fig. 1 shows typical light emitting sensors developed for the implementation of the OSV by which the various phenomena and movements can be monitored and visualized on site in real time. The monitoring items can be listed as follows at normal construction site.