EPI
EPI provides innovations for enhanced production in the subsurface energy industry that combine economic benefits and environmental sustainability. Energy Planning Innovation, working on innovations for government and university contracts.
July 25, 2021
Public Service Award
SPE Rocky Mountain North America Region awards the Regional Public Service Award for distinguished public service to Sidney Green and the Regional Service award to Dustin Doucet both here in Utah.
A B S T R A C T
The Geothermal Battery Energy Storage (“GB”) concept has been proposed as a large-scale renewable energy storage method. This has been discussed in a previous white paper by the same authors, “Geothermal Battery Energy Storage” April 2020, (download original white paper); in reservoir calculations by Palash, McLennan, and Green, “Reservoir Temperature and Pressure Profiles for Geothermal Battery Energy Storage in Sedimentary Basins”, ARMA 54th Annual Symposium, 20-A-1411-ARMA, June 2020; and in an on-line NSF sponsored workshop conducted by University of Utah on May 19, 2020, “Large-scale Subsurface Seasonal Solar Heat Storage for Future Value”. This work has created significant interest in the use of high porosity and high permeability rock formations for subsurface large-scale and long-term heat storage. It has also led to questions and considerations naturally arising regarding subsurface heat storage, which this paper addresses. Download full “questions” paper.
May 19, 2020
Large-scale Subsurface Seasonal Solar Heat Storage for Future Value virtual workshop
The workshop saw over 210 participants. A big thank you to the Department of Chemical Engineering at the University of Utah for hosting and organizing! We thank everyone for joining and hope it was valuable!
Click below for presenter contact info, slides and their comments:
Concept Overview………………………..Sidney Green….comments John McLennan..comments
Heat and Fluid Flow Calculations …..……..…. Palash Panja & John McLennan…slides..comments
Operational Considerations and Well Layouts ……..…......…. John McLennan….slides
Challenges of Sedimentary Basins …………………………..........…..…. Richard Allis.…slides
Site Potential from an Oil & Gas Industry Perspective ….…. Richard Newhart….slides..comments
Geochemical Considerations …………………………………….....….……. Joe Moore….slides…comments
Surface Facilities …………………………………….…………....………….…...…. Kevin Kitz.…slides
Facilitated Discussion and Summary ………………………....…..…. Sidney Green ….comments
Renewable Energy, published paper available via ScienceDirect (here) or preprint below the abstract:
Published paper:
Sidney Green1 ✉️, John Mclennan2, Palash Panja2, Kevin Kitz3, Rick Allis4 and Joseph Moore5
A B S T R A C T
The Geothermal Battery Energy Storage (“GB”) concept has been proposed as a large-scale renewable energy storage method. This is particularly important as solar and wind power are being introduced into electric grids, and economical utility-scale storage has not yet become available to handle the variable nature of solar and wind.
The Geothermal Battery Energy Storage concept uses solar radiance to heat water on the surface. The heated water is then injected deep into the earth. This hot water creates a high temperature geothermal reservoir acceptable for conventional geothermal electricity production, or for direct heat applications. Storing hot water underground is not a new idea, the unique feature of the GB is its application to sedimentary basins with formations that are water saturated and exhibit high porosity and high permeability. For certain reservoirs like these, calculations suggest that nearly one hundred percent of the stored heat can practically be recovered, and long-term, even seasonal storage is possible.
Several publications have been presented by the authors on the GB that parametrically identified desirable reservoir characteristics. This is a review of those calculations and the inferred conclusions for a viable GB system. Potential GB system well configurations, injection and production scenarios and ultimate heat recovery for economic value are noted. Download preprint publication.
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April 3, 2020
Gang Han’s Hydraulic Fracturing Community (HFC) "Robe Talk" series kicked off this week. The purpose of his series is to keep technical professionals engaged and stimulated while most are staying at home. The first presentation was US Shale Oil/Gas Recovery: A Drastic Change is Required, by Sidney Green.
Read the pdf. (Click on slide numbers in red to move between presentation text and slides)
Webex hosted and presented by Dr. Gang Han, @ARAMCOServices, and ARMA.
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October, 2019. We’ve been busy this fall! Sidney Green attended the US National Academy of Engineering annual meeting, presented a keynote at the 6th International Conference of Unconventional Geomechanics, and met with SINOPEC in Beijing. Bob and Jim spent time on triaxial testing services.
25th anniversary members - Members in attendance elected 25 years to the National Academy of Engineering (NAE).
This year the National Academy of Engineering’s (NAE) annual meeting highlighted 50 years of space travel, from the Apollo days to present, listen here to the NAE human space flight webcast. Sidney currently sits on the NAE Committee of Membership.
Following the early October academy meeting, in mid-October, the China University of Mining and Technology, Beijing, hosted the 6th International Conference on Unconventional Geomechanics (UG6) 更多.
UG6 Attendees.
The focus of UG6 was on the recovery of minerals from stacked deposits. Sidney Green presented a keynote lecture on the Recovery of Fluids from Layered Reservoirs (you can find the presentation here). A great, informative conference …another of Professor Jishan Liu’s continuously growing symposium series.
While in Beijing, Sidney also presented at SINOPEC Research Institute of Petroleum Engineering (Sripe) on geothermal and deep hard-rock geomechanic strategies and developments. Sripe is an affiliate of Sinopec Group. It is a world leader for wellbore technique research and development - a center for state-of-the-art petroleum engineering techniques. It's always such a pleasure to have time with such an engaged audience. Thank you Sripe and CUMTB for inviting EPI to give timely lectures and for incredible hospitality.
Baoping Zheng, Senior Engineer, The Research Institute of Petroleum Engineering, SINOPEC and Sidney Green, EPI. This view from the SINOPEC petroleum offices of the Bird’s Nest stadium and the mountains in the distance -amazing.
A special thank you to Wei Wang for hosting and being a great tour guide in Beijing. Mr. Wang is a Ph.D. candidate at China University of Mining and Technology, Beijing (CUMTB).
Finally, Bob Griffin and Jim Marquardt continue their calibration and certification of in-vessel instruments for geomechanics tests.
A busy season!
Hope everyone is enjoying the end of fall!
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EPI Question of the Month:
This Question-of-the-Month is about data delivery, data security, company policies and procedures, and most of all, making information available for its intended use as quickly as possible.
As the last step in the chain, what do managing all of these require to move testing & analysis results to productive applications, particularly in the current environment of big data?
Sherri Heroux, Data Management Specialist and former EPI Affiliate replies:
“Final report writing or analysis formatting is the last step to move test data and analysis to a commercial product. Based on many years of experience, this step is often taken for granted. It’s frequently just assumed that the data from tests and analyses get to a commercial product; but indeed, it doesn’t “just happen.” Recently, the emphasis on big data draws attention to the essential step of making data available in a user-friendly easily retrieval manner.
Geo-related data (lithology, mechanical/physical properties, in-situ stress, formation pressure etc) range from processed analog information from sensors that are converted to digital form, to qualitative observations of phenomena. Reliable information starts with the processing of sensor signals and requires careful archiving including provenance, calibrations, upsets, and procedures for generating and acquiring those data. That’s why input from the entire team is involved in this last step. “Bridging” between the test and analysis engineers and scientists and the end user clients is required. Quality control, data confidentiality, delivery schedules were always critical, and are even more so in the era of “big data.”
Over my experience of three decades managing and presenting geo-related data has evolved substantially. Initially, hard copy reports were prepared with appended analog presentations of data. Occasionally, an analyst made visual picks from charts. The data were usually summarized in a tabular form to emphasize key or anomalous behavior. We moved from this age of the IBM typewriter to prototype and progressively more sophisticated spreadsheets and word processing. This evolution offered improved hard copy reports and greatly facilitated rudimentary interpretive activities. Sharing and transmission of data was still laborious requiring mainly hard copies. Bandwidth was low; encryption was very basic and generally unnecessary, and transfer protocols were painful.
Lengthy data in flat files can now be provided to a client online, in color, and as 3D diagrams.
With time, electronic delivery of data developed, led by parallel developments of electronic transfer capabilities. Cost constraints favored transfer of tabulated information in flat files, with relational databases used only to a restricted extent. The transfer of data in this form, with implications for multi-million dollar financial decisions, caused quality assurance and data delivery security to become prime considerations.
What is the next frontier? Possibly the re-use of past data. As an example, miles and miles of rock core test data exist from past decades. That information may be available electronically, but not in a user-friendly and easily retrievable form. The bulk of these data has likely been underutilized if utilized at all. The volume of such data and the expenditures that would be required have precluded previous interpretation or even trend assessments. However, advanced computational capabilities using AI and machine learning are now aiming at using such data for modern oil/gas play developments, enhanced recovery assessments, and for vetting investment opportunities.
The opportunities for future data utilization are unfathomable. But, it’s still all about making information available as quickly as possible. That’s what “big data” is all about. What goes around, comes around...“
Sherri has extensive experience reporting and presenting rock data and analysis to end users. This requires bridging between engineers & scientists and end users while considering quality control, data management, technical writing, budget considerations, data confidentiality, delivery schedules, and other issues. For additional discussion she can be reached at sheroux @ epirecovery.com
EPI Question of the Month:
Jim, you are certainly an expert on laboratory triaxial rock testing, with many years of experience including assisting many rock mechanics laboratories and rock mechanics test data users, what do you think --even after decades of laboratory testing-- are the biggest reasons why there are considerable differences in the apparent rock properties measured by different laboratories?
REPLY from Jim Marquardt, EPI Affiliate
In my experience with a number of rock testing laboratories, indeed I do see considerable variations in the rock properties measured on similar rocks. The variations are not just rock variability, but tend to be either test problems and/or interpretation problems. Strength, shear stiffness and bulk compressibility, and ultra-sonic velocities all at varying confining pressures are among the most common properties measured. Measuring these properties under deep earth conditions is challenging. As one of my colleagues used to say, “if it was easy, everyone would do it”!
Jim Marquardt with triaxial test equipment.
One of the challenges is that rocks vary greatly in strength and stiffness, ranging from unconsolidated sandstones from the deep waters of the Gulf of Mexico, to quartzites encountered in the mining industry, to the all-important shale plays in North America. The first step for measuring properties over this broad range is proper testing system setup and calibration. For example, the range of the load cell and deformation measuring gages is critical. One would not want to use a fifty-thousand pound (50k lbf) load cell when measuring the strength of a 500 psi weak sandstone. Load at failure on a one-inch diameter sample would only be 1% of load-cell capacity.
Equally important is calibration of the instrumentation. One would not want to use a two hundred fifty thousand pound (250k lbf) class “A” instrument to calibrate the 50k lbf load cell noted above. Typically, third party calibration labs will provide a “10-point calibration”. Therefore by using the 250k lbf instrument to calibrate the 50k lbf load cell, only three data points would be utilized, 0, 25,000 and 50,000 pounds. It goes without saying that using that 50k lbf load cell calibrated with a 250k lbf instrument, for testing the weak sandstone noted above, is almost no calibration--yet I sometimes see this.
Measuring rock deformations is more difficult than measuring loads, and may be the source of the largest machine and interpretation problems. The entire "specimen stack" deforms under pressure and load, therefore requiring separating the sample deformation from the entire specimen stack deformation. This leads to Pressure Effect Corrections ("PE’s") and to Load Effect Corrections ("LE’s"). PE’s and LE’s are parameters that are typically directly measured on a standard material with known properties--such as aluminum, and applied either by hand or in the test computer software.
This is not easy, and to complicate matters, very small rock deformations can be involved, for example in measuring pore compressibility. The stiffer the rock and the smaller the sample, the more important these corrections become. And making things more difficult, PE's required for the deformation measuring transducers (inside the high-pressure environment) are not perfect. Transducer calibration tests can be made using a material with known properties (as noted above). But unfortunately, the small deformation of metals under pressure does not "exercise" the transducers to the extent as when deformations are made on the specimen stack. I have had experience with both strain-gauged cantilevers and with LVDT's for measuring the rock deformation. Each has its advantage and its limitations. Overall, rock testing laboratories must be equipped with a wide range of transducers and calibration instruments.
Specimen stack instrumentation.
Another area where I have seen errors has to do with the specimen stack and the test computer software aimed to "automatically" take into account the specimen stack, the rock, and the transducers. Since many things affect PE's and LE's, it is critical to maintain a compatible specimen stack, transducer, and test software. I have seen outright errors where something has changed in the setup (like changing transducers, changing endcaps, a repair on a strain gage, or even a different electrical connection) but no change has been made in the PE's or LE’s. Indeed, if these corrections are not properly determined and applied, incorrect apparent properties like Young's modulus, Poisson’s ratio, and bulk compressibility will be reported.
Finally, sample preparation, construction of the specimen stack, and test machine setup are critical. Proper techniques for all are difficult, and require trained individuals. Parallel sample ends, parallel specimen stack metal parts, and parallel machine alignment are required. The overall handling of the sample and placement of transducers are major aspects to be considered. Samples with voids or inclusions or fractures pose special problems as the analysis assumes that samples are statically determinant and that deformation is homogeneous throughout the sample. CT x-ray scans are very valuable to evaluate the quality of the sample prior to and after testing.
In conclusion, testing procedures and analysis of the recorded data determine the properties that are reported. I have seen cases of basic test procedure errors that lead to incorrect apparent properties. In other cases I have seen correct procedures but incorrect analysis of the recorded data. Specimen jacketing, endcap and spacer optimization, sample handling including moisture and temperature conditions, strain gage behavior, pre-loading of samples, and more.... are all details that lead to test scatter or to repeatable results. Experience teaches us that the details are critical! Thoughts anyone??
EPI Question of the Month:
Lab testing of rock samples is on recovered samples. Rock core that has been stress relieved, had pore fluids and temperature disturbed, and is then re-loaded in the lab to simulate reservoir conditions — How meaningful are these tests regarding representing the in-situ rock?
REPLY from Rico Ramos, former EPI Affiliate
In conventional reservoirs like sandstones and carbonates, decades of laboratory testing aided with field observations and history-matching, have shown good correlations between laboratory reservoir simulated tests and in-situ behavior. With unconventional shale reservoirs, laboratory tests are more challenging and need to be addressed.
Overall, the usual objective for the oil/gas industry laboratory rock testing programs has been to gather a set of values that bracket the range of expected in-situ properties. In some cases, the testing program may be as simple as to gather a property "index" representation, at an estimated reservoir simulated condition, to compare with other rock measured properties. Where time and costs are major limitations, reservoir simulation may not be made at all, particularly when the results can be scaled to certain boundary constraints. For the latter, the aim may simply be to measure quantities that could correlate with other measurement techniques--such as seismic and/or wireline logs, and then use these inferred properties, together with petrophysical properties, as inputs to analytical and numerical in-situ simulation models.
In all the cases, the meaningfulness, usefulness, and the value of the laboratory measured rock properties could be assessed based on three quality control (QC) criteria:
Repeatability of tests,
Ability to correlate with other measurements,
Ability to scale, spatially and as inputs to models of wells and reservoirs.
For repeatability, the measured properties for a given lithologic unit should fall into a 'tight' statistical bell curve. For the correlation with other measurements, a cross-check of core ultrasonic to log sonic velocities, the dynamic versus the static properties, the unconfined compressive strength to moduli are compared with petrophysical properties like porosity, permeability, and mineralogy. Comparing with the equivalent wireline log values using scatter x-plots and log-plots are handy graphic correlations. And ultimately, the laboratory results are scaled to wellbore or reservoir scale, by using the laboratory measured properties in simulator models--such as drilling, wellbore stability, subsidence, sand production, hydraulic fracturing and production simulations.
For the unconventional reservoir rocks, like shales, complexity is magnified making laboratory testing more demanding. They contain sub-micron multi-mineral components, large quantities of platy clays, organic matter, micro- to nano-meter porosity, and complex multi-phase in-situ pore fluids. On the macro scale, the rocks contain fine layers and sub-parallel interfaces, natural fractures and inclusions. The rocks tend to be highly anisotropic with nano-Darcy matrix permeability, and thinly-layered rock fabric, leading to heterogeneity at all scales.
Generally, typical conventional types of tests are performed across all rock types, shales, sandstones, and carbonates alike; including the same reservoir simulation procedures--basically confine the sample to the estimated reservoir and pore pressure stresses and sometimes to reservoir temperatures. As with conventional samples, linear elastic properties are inferred as for sandstones and carbonates--Young's modulus, Poisson's ratio, unconfined compressive strength, ultrasonic velocities, etc. And the three QC criteria of repeatability, ability to correlate with other measurements, and scalability, are also applied,
Even cognizant of the elements that distinguish shales, simulating reservoir conditions in laboratory tests haven't changed significantly. However, the rock testing programs have become more intensive and more tests are conducted, leading to higher costs. Large test-specimens and bigger test-populations are desired. Shales are very fragile, with large sample to sample variability, with high plugging failure rates, leading to higher degrees of sampling bias where more fragile specimens are eliminated from the testing matrix.
Because of the extremely low permeability of the shales, pore pressure equilibration during the test is difficult to impossible to achieve. To help ensure reliable and repeatable tests, longer test-periods (i.e. slower loading rates) are conducted. Rock creep trends to a patchy pore pressure distribution, particularly for the higher clay samples. Some cases require "live" pore fluids, making re-saturation more complicated.
Cross-correlations of mechanical properties (like Young's modulus, Poisson’s ratio) with other petrophysical properties show a mix of test scatter and intrinsic rock variability, all due to heterogeneity. Statistically trends of frequency scatter plots and cross plots of these mechanical properties, and of petrophysical properties (such as micro-porosity and nano-Darcy permeability), are widely dispersed with high standard deviations and low correlation coefficients. Special techniques like continuous core profiling, CT and micro-CT, penetrometers, rebound testing, and continuous core logging, have proven their usefulness in characterization and correlations. However, keep in mind that these measurements are on un-stressed samples at ambient conditions.
Sandstone core used for lab testing.
Scalability is a major concern because test samples are limited to plug dimensions, and the luxury of full-diameter cores are limited. Testing protocols can be designed considering rock heterogeneity, anisotropy, petrology, and petrophysics; such that the results, when used as input to gridded models, help bracket the range of expected in-situ responses.
Because of inherent rock variability and the discrepancies between laboratory capabilities and in-situ conditions, recommendations that rely on the laboratory tests may be qualified with the cautionary "P70-, P80-, P90- descriptors". These caveats are based on standard deviations, cross-correlation coefficients, and scaling modeling.
In conclusion, with any type of laboratory rock testing, there are uncertainties in results. Laboratory rock specimens are neither pristine nor restorable to exact virgin states. Even so, stringently applying the three quality control criteria of repeatability, ability to correlate with other measurement, and the ability to scale to in-situ conditions are essential. This reduces the uncertainties involved in their applications and adds confidence in their usage. This is especially true for complex formations like the unconventional shales.
January 11, 2019
“AI and Machine Learning: Propagating Rock Properties Using Filtered Drill Cuttings Analysis”
BACKGROUND: Within the oil and gas industry, artificial intelligence (AI) and machine learning to analyze large data sets generated by past activity are providing many advancements in exploration and production. Often this is simply referred to as "Big Data", which encompasses large amounts of data that are manipulated using AI and machine learning algorithms. At present this is primarily aimed at correlating well production with various factual data. However one refers to the subject, the end result is that large amounts of data can be used to make predictions, provide understandings of various phenomena and to solve complicated problems.
"Big Data" analysis currently most often considers clear observations such as lateral well drilling information, completion records, and well performance, with relatively little information of the details of the rock properties considered. To a large extent this is because details on the rock--particularly the rock heterogeneity--are not well known or understood, and yet can have profound influence on production. This makes integrating rock properties and heterogeneity into the "Big Data" workflow very important. Hence, propagation of formation measured rock properties to predict the rock where only limited rock data are available could be valuable and could be truly game changing.
Continue reading article...
by Sidney Green, Enhanced Production, Inc., Patrick Gathogo, Alexander Nadeev, Rock Microscopy LLC.
We continue focusing on research, engineering, and consulting-advising.
During 2018, EPI pursued improving the efficiency of hydraulic fracturing for the recovery of oil/gas from unconventional resources.
A technical presentation was given by Sidney Green at the 52nd US Rock Mechanics/ Geomechanics ARMA Symposium (www.epirecovery.com/news June, 2018) and an abstract has been submitted for presentation at ARMA 2019. Stay tuned for details.
Geothermal energy heating a pool, Iceland.
Also during 2018, EPI continued development of the Geothermal Battery Energy Storage concept in collaboration with the Idaho National Laboratory and Prof. McLennan at the Univ. of Utah. Further funding for the concept is expected in early 2019 from the National Science Foundation via the Univ. of Utah with Co-Principal Investigators Prof. McLennan and Sidney Green.
June 1, 2018
”Early Time Fracture Growth and Cluster Spacing Effects” by S. Green, G. Xu, B. Forbes, J. McLennan, G. Green, D. Work is accepted for the ARMA Annual Symposium in Seattle. Sidney Green will present the paper during the podium presentation, Tuesday June 19th, in the Technical Session track - Hydraulic Fracturing Geomechanics II.
ABSTRACT: The injection of large quantities of treating fluid and proppants during fracture stimulation of low permeability formations causes local insitu stress changes, sometimes referred to as stress shadowing or stress interference. Recent procedures for improving production have led to closer spacing of clusters, from approximately 80 feet spacing a few years ago to about 20 feet spacing now, or less in some cases. That is, there are now about four times the number of potential fracture initiation locations (clusters) per foot of lateral well, while the sand pumped per foot of lateral continues at about 1700-1800 pounds per foot. With four times the number of clusters and the same mass of sand pumped, the stress disturbance of one cluster to another cluster has changed. This paper addresses the near wellbore stress interference effects for close cluster spacing. Numerical simulations are presented using a robust linear-elastic 3-D hydraulic fracturing computer code that calculates fracture ‘bending’ and fracture width change due to stress interference. The stress interference that changes the fracture width is the most significant because the resistance to fracture fluid flow at high velocities in these narrow channels is the primary driver of stress shadowing fracture geometry changes. Continue..
April 23, 2018
Sidney Green recently presented at George Washington University at the US Association of Energy Economics, National Capital Area Chapter, 22nd Annual Washington Energy Policy Conference on "Energy Technologies and Innovations: A Disturbance in the [Market] Force".
He served on the Panel "Hydrocarbons Strike Back: Innovations to Maintain the Status Quo", and presented "Upstream Innovations in Shale Production". His Panel remarks can be read here.
October, 2017
Zhaofeng Zhang, General Manager of CNPC GreatWall Drilling and Dr. GenSheng Li, VP of China University of Petroleum Beijing, and member of the Chinese Academy of Engineering and others visit EPI for geothermal energy discussions.
China is pursuing significant research with the goal of increasing geothermal efficiency and the new concept of Geothermal Battery Energy Storage. China University of Petroleum and EPI agreed to pursue a joint drilling improvement cooperation, and an MOU is being developed.
click to download full paper
September, 2017
EPI brings in Dr. Alex Xu, developer and President of FrackOptima to present at the University of Utah, Energy & Geoscience Institute on the details of using simulation analysis software prior to in situ production....
EPI staff and Alex Xu.
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From the article: "Despite not fully understanding the basic physics of fluid flowing through shale rocks, industry has nonetheless found a way to recover the oil."
August 9, 2017
Upstream Technology Magazine publishes an interview with Sid Green at EPI discussing factors effecting shale oil recovery.
Despite not fully understanding the basic physics of fluid flowing through shale rocks, industry has nonetheless found a way to recover the oil. Cracking the code in tight shale.
Oil moves through shale rocks, even though the physical structure of such rocks suggests it should not. That is only one of the confusing aspects to consider when developing the shale oil plays, according to experts in the rock mechanics field….
June 25, 2017
Solar energy, and to a lesser extent wind energy, have moved ahead of the ability to manage their intermittent nature without similar growth in cost effective energy storage.
On June 24, Sidney Green chaired a meeting on large-scale energy storage that could be used to support solar and wind electricity. The meeting was supported by the National Science Foundation, Geothermal Energy SedHeat Program with cooperation of the American Rock Mechanics Association.
The small invited group considered a concept of solar thermal underground energy storage.
Underground storage competes with surface heat storage in tanks, and is more complicated then surface storage in some ways. However, for large-scale Gigawatt hours of energy storage, underground storage may be more practical and cost effective at least in some situations.
The full Report is available online here.
June 7, 2017
EPI hosted Dr. Sau-Wai Wong, geomechanics expert and consultant June 6-7, 2017. Dr. Wong during his EPI visit, spoke at the SPE Salt Lake Section meeting June 7th. His presentation, "Past Achievements and Recent Research Activities in Petroleum Geomechanics" described key achievements in practical petroleum geomechanics over the past few years. The SPE meeting was held at the University of Utah EGI office in Research Park.
Dinner afterwards. Sau-Wai Wong, Sid Green, John McLennan
Sidney Green is senior author on a paper accepted for the ARMA 51st US Rock Mechanics / Geomechanics Symposium. June 25-28, 2017.
"Hydraulic Fracture Propagation in Steps Considering Different Fracture Fluids", by Sidney Green(1), Joseph Walsh(2), John McLennan(3), Bryan Forbes(4). Click title to read abstract.
(1 Enhanced Production, Inc. & University of Utah, 2 Retired MIT, 3 University of Utah, 4 Consultant).
