Geothermal reservoir monitoring with a combination of absolute and relative gravimetry

Geophysics ◽  
2008 ◽  
Vol 73 (6) ◽  
pp. WA37-WA47 ◽  
Author(s):  
Mituhiko Sugihara ◽  
Tsuneo Ishido
Keyword(s):  
History Matching ◽  
Observation Interval ◽  
Time Lapse ◽  
Gravity Measurement ◽  
Absolute Gravity ◽  
Short Term ◽  
Well Production ◽  
Gravity Measurements ◽  
Central Production

Microgravity monitoring is a valuable tool for mapping the redistribution of subsurface mass and for assessing changes in fluid recharge from reservoir boundaries associated with geothermal exploitation. To further the development of a high-precision absolute/relative hybrid gravity-measurement technique, we conducted measurements using an absolute gravimeter in two geothermal fields in Japan. The absolute gravity measurements were performed in the central production areas to directly measure gravity changes caused by fluid withdrawal. We succeeded in measuring long-term trends within an accuracy of a few microgals in the Okuaizu and Ogiri fields, which have been producing electricity for several years. Absolute measurements in the center of the field provide reliable and local reference datum anchor points for more widely distributed relative gravity measurements. In the Ogiri field, we carried out time-lapse hybrid measurements with this combination of absolute and relative gravimetry and delineated the spatial distributions of long- and short-term changes. The long-term changes are relatively small, considering the four-year observation interval. This suggests a near balance between the mass withdrawal rate from wells and mass recharge from peripheral regions. The apparent balance is reproduced fairly well by a preliminary numerical reservoir simulation study. The observed long- and short-term changes are thought to be useful constraints for planned history-matching studies based on refined reservoir models with greater spatial resolution that incorporate detailed well-by-well production histories.

A Compound Recoil-Compensated Chamber Design for Free-Fall Absolute Gravimeters

2020 ◽  
Author(s):  
Yi Wen ◽  
Kang Wu ◽  
Meiying Guo ◽  
Lijun Wang
Keyword(s):  
High Precision ◽  
Free Fall ◽  
Test Mass ◽  
Precision Measurements ◽  
Gravity Measurement ◽  
Absolute Gravity ◽  
Systematic Bias ◽  
Chamber Design ◽  
Measurement Results ◽  
Gravity Measurements

Abstract The ballistic free-fall absolute gravimeters are most commonly-used instruments for high-precision absolute gravity measurements in many fields, such as scientific research, resource survey, geophysics and so on. The instrumental recoil vibrations generated by the release of the test mass can cause troublesome systematic bias, because these vibrations are highly reproducible from drop to drop with coherent phase. A compound counterbalanced design of chamber using both belt-driven mechanism and cam-driven structure is proposed in this paper. This structure is designed to achieve excellent recoil compensation as well as long freefall length for high precision measurements. Simulation results show that the recoil vibration amplitude of the compound recoil-compensated structure during the drop is about 1/4 of that with only belt-driven counterbalanced structure. This confirms the feasibility and superiority of the new design. And it is believed that the absolute gravimeter based on this newly proposed chamber design is expected to obtain more precise gravity measurement results in the future.

scholarly journals Performance of three iGrav superconducting gravity meters before and after transport to remote monitoring sites

2020 ◽  
Vol 223 (2) ◽  
pp. 959-972
Author(s):  
Florian Schäfer ◽  
Philippe Jousset ◽  
Andreas Güntner ◽  
Kemal Erbas ◽  
Jacques Hinderer ◽  
...  
Keyword(s):  
Geothermal Field ◽  
Absolute Gravity ◽  
Absolute Calibration ◽  
Noise Levels ◽  
Before And After ◽  
Gravity Measurements ◽  
Superconducting Gravity ◽  
The Stability ◽  
Comparison Measurements

SUMMARY High spatial and temporal resolution of gravity observations allows quantifying and understanding mass changes in volcanoes, geothermal or other complex geosystems. For this purpose, accurate gravity meters are required. However, transport of the gravity meters to remote study areas may affect the instrument's performance. In this work, we analyse the continuous measurements of three iGrav superconducting gravity meters (iGrav006, iGrav015 and iGrav032), before and after transport between different monitoring sites. For 4 months, we performed comparison measurements in a gravimetric observatory (J9, Strasbourg) where the three iGravs were subjected to the same environmental conditions. Subsequently, we transported them to Þeistareykir, a remote geothermal field in North Iceland. We examine the stability of three instrumental parameters: the calibration factors, noise levels and drift behaviour. For determining the calibration factor of each instrument, we used three methods: First, we performed relative calibration using side-by-side measurements with an observatory gravity meter (iOSG023) at J9. Secondly, we performed absolute calibration by comparing iGrav data and absolute gravity measurements (FG5#206) at J9 and Þeistareykir. Thirdly, we also developed an alternative method, based on intercomparison between pairs of iGravs to check the stability of relative calibration before and after transport to Iceland. The results show that observed changes of the relative calibration factors by transport were less than or equal to 0.01 per cent. Instrumental noise levels were similar before and after transport, whereas periods of high environmental noise at the Icelandic site limited the stability of the absolute calibration measurements, with uncertainties above 0.64 per cent (6 nm s–2 V–1). The initial transient drift of the iGravs was monotonically decreasing and seemed to be unaffected by transport when the 4K operating temperatures were maintained. However, it turned out that this cold transport (at 4 K) or sensor preparation procedures before transport may cause a change in the long-term quasi-linear drift rates (e.g. iGrav015 and iGrav032) and they had to be determined again after transport by absolute gravity measurements.

scholarly journals VOLUME DEFORMATION VARIATIONS AND WELL-AQUIFER RESPONSE, ITS CONNECTION WITH GRAVITY MEASUREMENTS

2021 ◽  
Vol 26 (5) ◽  
pp. 40-51
Author(s):  
Vladimir Yu. Timofeev ◽  
◽  
Dmitriy G. Ardyukov ◽  
Anton V. Timofeev ◽  
Pavel Yu. Gornov ◽  
...  
Keyword(s):  
Water Level ◽  
Barometric Pressure ◽  
Earth Tides ◽  
Water Level Fluctuations ◽  
Gravity Measurement ◽  
Absolute Gravity ◽  
Volume Deformation ◽  
Level Data ◽  
Gravity Measurements ◽  
Tidal Signal

Precise gravity measurements at g0·10 -9 level requires taking into account density change, caused by the Earth’s crust deformation and the movement and position of the fluid in the layer. The paper presents analysis of water level observation in three boreholes situated at Primorie, at Kamchatka and at Baikal region. Water-level fluctuations were influenced by earth tides, barometric pressure, co-seismic effects and season precipitations. Water tidal signal was analyzed for calculations of level-strain coefficients, its values changed from 0.1 mm/10-9 to 1.6 mm/10-9. Gravity corrections were developed by volume variation. For borehole drilled at monolithic rock we used the phaselag effect for tidal strain and crack-system orientation was studied in Pribaikalie mountain valley. Longterm gravity results were tested with water level data at Talaya station (Pribaikalie). Talaya gravity point situated at monolithic rock had no influence from water level variation. Level-correction was less than absolute gravity measurement error. Quick coseismic effects of earthquakes are well registered by level measuring, deformation graphical and absolute gravimetric methods.

New gravity control in Poland – needs, the concept and the design

2013 ◽  
Vol 62 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Jan Krynski ◽  
Tomasz Olszak ◽  
Marcin Barlik ◽  
Przemyslaw Dykowski
Keyword(s):  
Environmental Changes ◽  
Geodetic Network ◽  
International Standards ◽  
Gravity Measurement ◽  
Reference Level ◽  
Absolute Gravity ◽  
Gravity Gradient ◽  
Base Points ◽  
Vertical Gravity Gradient ◽  
Gravity Measurements

Abstract The existing Polish gravity control (POGK) established in the last few years of 20th century according to the international standards is spanned on 12 absolute gravity stations surveyed with four different types of absolute gravimeters. Relative measurements performed by various groups on nearly 350 points of POGK with the use of LaCoste&Romberg (LCR) gravimeters were linked to those 12 stations. The construction of the network, in particular the limited number of non homogeneously distributed absolute gravity stations with gravity determined with different instruments in different epochs is responsible for systematic errors in g on POGK stations. The estimate of those errors with the use of gravity measurements performed in 2007-2008 is given and their possible sources are discussed. The development of absolute gravity measurement technologies, in particular instruments for precise field absolute gravity measurements, provides an opportunity to establish new type of gravity control consisting of stations surveyed with absolute gravimeters. New gravity control planned to be established in 2012-2014 will consist of 28 fundamental points (surveyed with the FG5 - gravimeter), and 169 base points (surveyed with the A10 gravimeter). It will fulfill recent requirements of geodesy and geodynamics and it will provide good link to the existing POGK. A number of stations of the new gravity control with precisely determined position and height will form the national combined geodetic network. Methodology and measurement schemes for both absolute gravimeters as well as the technology for vertical gravity gradient determinations in the new gravity control were developed and tested. The way to assure proper gravity reference level with relation to ICAG and ECAG campaigns as well as local absolute gravimeter comparisons are described highlighting the role of metrology in the project. Integral part of the project are proposals of re-computation of old gravity data and their transformation to a new system (as 2nd order network) as well as a definition of gravity system as “zero-tide” system. Seasonal variability of gravity has been discussed indicating that the effects of environmental changes when establishing modern gravity control with absolute gravity survey cannot be totally neglected.

A New Decline-Curve-Analysis Method for Layered Reservoirs

SPE Journal ◽  
2020 ◽  
Vol 25 (04) ◽  
pp. 1657-1669
Author(s):  
Kittiphong Jongkittinarukorn ◽  
Nick Last ◽  
Freddy Humberto Escobar ◽  
Kreangkrai Maneeintr
Keyword(s):  
Flow Rate ◽  
History Matching ◽  
Oil And Gas ◽  
Single Layer ◽  
Short Term ◽  
Reserve Estimation ◽  
Early Stages ◽  
Decline Curve ◽  
Decline Rate

Summary This study presents a new method to improve production forecasts and reserve estimation for a multilayer well in the early stages of production using the Arps (1945) hyperbolic decline method to model the decline rate of each layer. The method can be applied to both oil and gas wells. The new approach generates the profiles of the instantaneous decline rate (D) and instantaneous decline-curve exponent (b) from the historical flow rate (q). Because of the inherent noise in the production data, a regression technique is applied to smooth the flow-rate data, and the analysis is performed on the smoothed data. History matching is performed not only on the profile of q but also on the profiles of D and b. This results in the unique decline parameters (qi,Di, and b) for each layer. For a multilayer well, the values of D and b vary with time, which means that the well's performance cannot be modeled using a conventional single-layer-well approach. Furthermore, the well-known nonuniqueness problem from history matching is magnified in a multilayer well: Many models can successfully match the production profile in the short-term but fail to match it in the longer term. Only the correct model can match the profiles of q, D, and b over both the short-term and the long-term. The proposed method provides the correct unique decline parameters (qi,Di, and b) for each layer, during the early stages of production, and these parameters are then valid for the life of the well. The method works well for both synthetic examples and actual field data. The novelty of the new methodology is the ability to provide the decline parameters for each layer at an early stages of production that can then be used for production forecasting in the long-term. The nonuniqueness problem from history matching is solved.

scholarly journals Thirty years of precise gravity measurements at Mt. Vesuvius: an approach to detect underground mass movements

2013 ◽  
Vol 56 (4) ◽  
Author(s):  
Giovanna Berrino ◽  
Vincenzo d’Errico ◽  
Giuseppe Ricciardi
Keyword(s):  
Ground Deformation ◽  
Reference Station ◽  
Absolute Gravity ◽  
Volcanic Area ◽  
Gravity Station ◽  
Gravity Changes ◽  
Gravity Measurements ◽  
Elevation Changes ◽  
Gravity Network

<p>Since 1982, high precision gravity measurements have been routinely carried out on Mt. Vesuvius. The gravity network consists of selected sites most of them coinciding with, or very close to, leveling benchmarks to remove the effect of the elevation changes from gravity variations. The reference station is located in Napoli, outside the volcanic area. Since 1986, absolute gravity measurements have been periodically made on a station on Mt. Vesuvius, close to a permanent gravity station established in 1987, and at the reference in Napoli. The results of the gravity measurements since 1982 are presented and discussed. Moderate gravity changes on short-time were generally observed. On long-term significant gravity changes occurred and the overall fields displayed well defined patterns. Several periods of evolution may be recognized. Gravity changes revealed by the relative surveys have been confirmed by repeated absolute measurements, which also confirmed the long-term stability of the reference site. The gravity changes over the recognized periods appear correlated with the seismic crises and with changes of the tidal parameters obtained by continuous measurements. The absence of significant ground deformation implies masses redistribution, essentially density changes without significant volume changes, such as fluids migration at the depth of the seismic foci, i.e. at a few kilometers. The fluid migration may occur through pre-existing geological structures, as also suggested by hydrological studies, and/or through new fractures generated by seismic activity. This interpretation is supported by the analyses of the spatial gravity changes overlapping the most significant and recent seismic crises.</p>

Iceberg dynamics in a proglacial lake in Austria quantified by time-lapse photography

2021 ◽  
Author(s):  
Felix Bernsteiner ◽  
Andreas Kellerer-Pirklbauer
Keyword(s):  
Time Lapse ◽  
European Alps ◽  
Weather Station ◽  
Lake Surface ◽  
Short Term ◽  
Proglacial Lakes ◽  
Proglacial Lake ◽  
Term Analysis ◽  
Lake Margin

&lt;p&gt;The recession of glaciers reveals a dynamic landscape exposed to high rates of hydrological and geomorphological modifications. Such deglaciation processes caused the formation of a 0.3 km&amp;#178; large proglacial lake (named Pasterzensee) near the terminus of Pasterze Glacier, Austria, during the last two decades. The evolution of the proglacial lake was accompanied by several buoyant calving events. The process of buoyant calving formed numerous floating dead ice bodies referred to as icebergs which covered a maximum of 7.3 % of the entire proglacial lake basin in November 2018.&lt;/p&gt;&lt;p&gt;Despite the existence of icebergs at some proglacial lakes in the European Alps, little is known about the evolution and life span of icebergs in proglacial lakes in the European Alps. The aim of this study was to reduce this research gap by (a) quantifying the evolution of such alpine icebergs during two different time scales and by (b) analysing the relationship between iceberg evolution and motion at the lake with meteorological conditions. At a long-term scale, one single iceberg was monitored during the period 01.09.2017-30.09.2019. At a short-term scale, all icebergs were studied during one single day (16.06.2019).&lt;/p&gt;&lt;p&gt;The most important data source for this study were time-lapse optical imagery from an automatic camera overlooking the entire proglacial lake (GROHAG). The used camera is a Roundshot Livecam Generation 2 (Seitz, Switzerland). Photographic imagery is captured every five minutes (during daylight) from a location 310 m above lake level and 450 m northeast of the lake margin. For the long-term analysis, a total number of 386 pictures of the lake were processed. For the short-term analysis, 97 pictures were analysed to reveal the dynamics of 84 icebergs during one single day. The oblique time-lapse images were transformed into orthorectified photos using a rectification algorithm which considers the camera properties and the lake surface geometry. Iceberg size and centroid coordinates were mapped in all generated orthophotos. In addition, meteorological data (ZAMG Vienna) was provided by a nearby automatic weather station, located at the glacier tongue of Pasterze Glacier some 1.1 km northwest of the lake margin.&lt;/p&gt;&lt;p&gt;Results indicate that the monitoring of one iceberg over a period of 25 months revealed highest melting rates from June to August, low melting rates from September to November and no measurable melting when the lake surface is frozen. Horizontal iceberg displacement is rising with decreasing iceberg size throughout the study period. The analysed iceberg formed during the detachment of a debris covered ice peninsula with an initial size of 7250 m&amp;#178; and was last identifiable at a size of 240 m&amp;#178;. Monitoring lake-wide iceberg movement for one day shows that wind is the main influence on horizontal iceberg displacement. The existence of a strong valley wind, caused by a diurnal warming cycle, is observed. This wind system decouples the iceberg movement from the constant katabatic glacier wind, recorded by the weather station. Frequent jumps in movement rates, which are not explained by wind data, suggest that iceberg grounding is a common process influencing subaquatic lake morphology.&lt;/p&gt;

The 4D microgravity method for waterflood surveillance: Part II — Gravity measurements for the Prudhoe Bay reservoir, Alaska

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. I33-I43 ◽  
Author(s):  
J. F. Ferguson ◽  
T. Chen ◽  
J. Brady ◽  
C. L. Aiken ◽  
J. Seibert
Keyword(s):  
Water Injection ◽  
Time Lapse ◽  
Lessons Learned ◽  
The Arctic ◽  
Absolute Gravity ◽  
Theoretical Investigations ◽  
Gravity Measurements ◽  
Series Of Experiments ◽  
Prudhoe Bay ◽  
Relative Gravimeter

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.

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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