Erika Gasperikova

Direct reservoir parameter estimation using joint inversion of marine seismic AVA and CSEM data

A new joint inversion algorithm to directly estimate reservoir parameters is described. This algorithm combines seismic amplitude versus angle (AVA) and marine controlled source electromagnetic (CSEM) data. The rock-properties model needed to link the geophysical parameters to the reservoir parameters is described. Errors in the rock-properties model parameters, measured in percent, introduce errors of comparable size in the joint inversion reservoir parameter estimates. Tests of the concept on synthetic one-dimensional models demonstrate improved fluid saturation and porosity estimates for joint AVA-CSEM data inversion (compared to AVA or CSEM inversion alone). Comparing inversions of AVA, CSEM, and joint AVA-CSEM data over the North Sea Troll field, at a location with well control, shows that the joint inversion produces estimated gas saturation, oil saturation and porosity that is closest (as measured by the RMS difference, L1 norm of the difference, and net over the interval) to the logged values whereas CSEM inversion provides the closest estimates of water saturation.

Gravity monitoring of CO2 movement during sequestration : Model studies

Sequestration/enhanced oil recovery EOR petroleum reservoirs have relatively thin injection intervals with multiplefluidcomponentsoil,hydrocarbongas,brine,andcarbon dioxide, or CO2, whereas brine formations usually have much thicker injection intervals and only two components brine and CO2. Coal formations undergoing methane extractiontendtobethin3‐10 mbutshallowcomparedtoeitherEORorbrineformations.InjectingCO2intoanoilreservoir decreases the bulk density in the reservoir. The spatial pattern of the change in the vertical component of gravity Gz is correlated directly with the net change in reservoir density. Furthermore, time-lapse changes in the borehole Gz clearlyidentifytheverticalsectionofthereservoirwherefluidsaturationsarechanging.TheCO2-brinefront,ontheorder of1 kmwithina20-m-thickbrineformationat1900-mdepth with 30% CO2 and 70% brine saturations, respectively, produceda 10-Galsurfacegravityanomaly.Suchananomaly would be detectable in the field. The amount of CO2 in a coal-bed methane scenario did not produce a large enough surface gravity response; however, we would expect that for an industrial-size injection, the surface gravity response wouldbemeasurable.Gravityinversionsinallthreescenarios illustrate that the general position of density changes causedbyCO2canberecoveredbutnottheabsolutevalueof thechange.Analysisofthespatialresolutionanddetectability limits shows that gravity measurements could, under certaincircumstances,beusedasalower-costalternativetoseismicmeasurements.

Monitoring protocols and life-cycle costs for geologic storage of carbon dioxide

Publisher Summary Every geologic storage project goes through a series of phases which constitute the life-cycle of the project. During each of these phases, monitoring serves different purposes. This chapter suggests that there are four distinct phases of life-cycle of a geologic storage project: a pre-operation phase, an operational phase, a closure phase and a post-closure phase. Key assumptions underlying the cost estimates such as reservoir size and depth are provided and major cost dependencies are also described. For each scenario a “package” of suitable monitoring techniques is proposed with a commentary on how the components were selected. For each monitoring scenario a basic and enhanced monitoring program is evaluated. Estimated costs for monitoring geologic storage over the full life-cycle of a project at a range from

UXO detection and identification based on intrinsic target polarizabilities: A case history

0.05 to

Long-term electrical resistivity monitoring of recharge-induced contaminant plume behavior.

0.10 per ton of CO2. The chapter summarizes one part of a study performed for the International energy agency greenhouse gas R&D program (IEA GHG) to provide an overview of monitoring techniques for geologic storage of CO2.

A feasibility study of nonseismic geophysical methods for monitoring geologic CO2 sequestration

Electromagnetic induction data parameterized in time dependent object intrinsic polarizabilities allow discrimination of unexploded ordnance (UXO) from false targets (scrap metal). Data from a cart-mounted system designed for discrimination of UXO with 20 mm to 155 mm diameters are used. Discrimination of UXO from irregular scrap metal is based on the principal dipole polarizabilities of a target. A near-intact UXO displays a single major polarizability coincident with the long axis of the object and two equal smaller transverse polarizabilities, whereas metal scraps have distinct polarizability signatures that rarely mimic those of elongated symmetric bodies. Based on a training data set of known targets, object identification was made by estimating the probability that an object is a single UXO. Our test survey took place on a military base where both 4.2-inch mortar shells and scrap metal were present. The results show that we detected and discriminated correctly all 4.2-inch mortars, and in that process we added 7%, and 17%, respectively, of dry holes (digging scrap) to the total number of excavations in two different survey modes. We also demonstrated a mode of operation that might be more cost effective than the current practice.

Sensitivity and Cost of Monitoring Geologic Sequestration Using Geophysics

Geophysical measurements, and electrical resistivity tomography (ERT) data in particular, are sensitive to properties that are related (directly or indirectly) to hydrological processes. The challenge is in extracting information from geophysical data at a relevant scale that can be used to gain insight about subsurface behavior and to parameterize or validate flow and transport models. Here, we consider the use of ERT data for examining the impact of recharge on subsurface contamination at the S-3 ponds of the Oak Ridge Integrated Field Research Challenge (IFRC) site in Tennessee. A large dataset of time-lapse cross-well and surface ERT data, collected at the site over a period of 12 months, is used to study time variations in resistivity due to changes in total dissolved solids (primarily nitrate). The electrical resistivity distributions recovered from cross-well and surface ERT data agrees well, and both of these datasets can be used to interpret spatiotemporal variations in subsurface nitrate concentrations due to rainfall, although the sensitivity of the electrical resistivity response to dilution varies with nitrate concentration. Using the time-lapse surface ERT data interpreted in terms of nitrate concentrations, we find that the subsurface nitrate concentration at this site varies as a function of spatial position, episodic heavy rainstorms (versus seasonal and annual fluctuations), and antecedent rainfall history. These results suggest that the surface ERT monitoring approach is potentially useful for examining subsurface plume responses to recharge over field-relevant scales.

Non-Seismic Geophysical Approaches to Monitoring

Because of their wide application within the petroleum industry it is natural to consider geophysical techniques for monitoring of CO2 movement within hydrocarbon reservoirs, whether the CO2 is introduced for enhanced oil/gas recovery or for geologic sequestration. Among the available approaches to monitoring, seismic methods are by far the most highly developed and applied. Due to cost considerations, less expensive techniques have recently been considered. In this article, the relative merits of gravity and electromagnetic (EM) methods as monitoring tools for geological CO2 sequestration are examined for two synthetic modeling scenarios. The first scenario represents combined CO2 enhanced oil recovery (EOR) and sequestration in a producing oil field, the Schrader Bluff field on the north slope of Alaska, USA. The second scenario is a simplified model of a brine formation at a depth of 1,900 m.

Natural field induced polarization for mapping of deep mineral deposits: A field example from Arizona

Publisher Summary Monitoring of geologic sequestration projects will be needed to manage the process of filling the reservoir, verify the amount of CO2 sequestered in a particular volume, and detect leaks. It is natural to consider geophysical techniques because of the large body of experience in their application in the petroleum industry. The scale of sequestration projects will be similar to or greater than that of petroleum reservoirs. With current technology, the only practical approach to achieving the required spatial coverage at reservoir scale is the use of surface techniques. High-resolution wellbore and inter-well (crosswell) geophysics will be part of a monitoring program, but these methods are either limited to sampling near the wellbore or currently too expensive to consider for monitoring of the entire reservoir volume. Surface reflection seismic is the most highly developed surface geophysical technique. It is used more often in the petroleum industry, primarily because of its high spatial resolution compared to other surface techniques. The sensitivity of geophysical methods depends, first of all, on the contrast in geophysical properties produced by introduction of CO2. Models of rock physics were used to calculate anticipated contrasts in seismic velocity and impedance in brine saturated rock when CO2 is introduced. The phase behavior of CO2 has large effects on property contrasts over the depth and temperature range of interest in geologic sequestration projects. Detectability depends critically on the spatial resolution of the method. Numerical simulations were performed to evaluate how small a volume of CO2 could be detected in the subsurface by seismic methods.

Integration of Marine CSEM And Seismic AVA Data For Reservoir Parameter Estimation

This chapter deals with the application of a number of different geophysical techniques for monitoring geologic storage of CO 2 . The relative merits of the seismic, gravity, electromagnetic (EM) and streaming potential (SP) geophysical techniques as monitoring tools are examined. The chapter evaluates the capabilities of a number of geophysical techniques on two synthetic modeling scenarios. The first scenario represents combined CO 2 enhance oil recovery (EOR) and storage in a producing oil field, the Schrader Bluff field on the north slope of Alaska, USA. The second scenario is of a pilot DOE CO 2 storage experiment scheduled for summer 2004 in the Frio Brine Formation in South Texas, USA. Numerical flow simulations of the CO 2 injection process for each case were converted to geophysical models using petrophysical models developed from well log data. These coupled flow simulation-geophysical models allow comparison of the performance of monitoring techniques over time on realistic 3D models by generating simulated responses at different times during the CO 2 injection process. These time-lapse measurements are used to produce time-lapse changes in geophysical measurements that can be related to the movement of CO 2 within the injection interval.