Lehua Pan

T2Well—An integrated wellbore–reservoir simulator

At its most basic level, management of subsurface fluid resources involves a system comprising the wellbore and the target reservoir. As discrete pathways through geologic formations, boreholes and wells are critical to the success of many water, energy, and environmental management operations. Although many stand-alone simulators for two-phase flow in wellbores with various levels of sophistication have been developed, simulating non-isothermal, multiphase, and multi-component flows in both the wellbore and in the porous or fractured media reservoir as an integrated system remains a challenging yet important task. The difficulties include (1) different governing equations apply to the wellbore and the reservoir that need to be solved efficiently in a uniform framework, (2) the significant contrast in temporal and spatial scales between the wellbore and the reservoir that results in a very challenging set of stiff partial differential equations, and (3) other complexities (e.g., dry-out) that can be caused by flow processes between the wellbore and the reservoir. To address the need to simulate coupled wellbore-reservoir flow, we have developed T2Well, a numerical simulator for non-isothermal, multiphase, and multi-component flows in the integrated wellbore-reservoir system. The new model extends the existing numerical reservoir simulator TOUGH2 to calculate the flow in both the wellbore and the reservoir simultaneously and efficiently by introducing a special wellbore sub-domain into the numerical grid. For grid blocks in the wellbore sub-domain, we solve the 1D momentum equation of the mixture (which may be two-phase) as described by the drift-flux model (DFM). A novel mixed implicit-explicit scheme for friction in the wellbore is applied to facilitate the solution of the momentum equation, while other variables are calculated fully implicitly. Applications of the new simulator to problems in various fields are presented to demonstrate its capabilities.

Determination of particle transfer in random walk particle methods for fractured porous media

A commonly used numerical scheme to simulate solute transport in the subsurface is the random walk particle method (RWPM). While significant progress has been made in developing random walk particle algorithms for porous media, an RWPM for fractured porous media, represented by dual continua, has not yet been developed in the literature. A key issue in developing an RWPM for fractured porous media is the determination of particle transfer between the two continua. In this study a relatively simple, yet physically based scheme to determine the particle transfer is developed. The usefulness of the scheme is demonstrated by comparing solute transport results determined from the proposed scheme with (1) an analytical solution for solute transport in a fractured porous medium with parallel fractures and (2) a numerical simulation obtained using the TOUGH2 code, a simulator for multiphase and multicomponent flow and transport in fractured porous media.

T2Well/ECO2N Version 1.0: Multiphase and Non-Isothermal Model for Coupled Wellbore-Reservoir Flow of Carbon Dioxide and Variable Salinity Water

LBNL-4291E T2Well/ECO2N Version 1.0: Multiphase and Non-Isothermal Model for Coupled Wellbore-Reservoir Flow of Carbon Dioxide and Variable Salinity Water Lehua Pan, Curtis M. Oldenburg, Yu-Shu Wu * and Karsten Pruess Earth Sciences Division Lawrence Berkeley National Laboratory University of California Berkeley, CA 94720 February 14, 2011 This work was supported in part by the CO 2 Capture Project (CCP) of the Joint Industry Program (JIP), by the National Risk Assessment Partnership (NRAP) through the National Energy Technology Laboratory, and by Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231. *Currently at Colorado School of Mines

Numerical simulations of the Macondo well blowout reveal strong control of oil flow by reservoir permeability and exsolution of gas.

In response to the urgent need for estimates of the oil and gas flow rate from the Macondo well MC252-1 blowout, we assembled a small team and carried out oil and gas flow simulations using the TOUGH2 codes over two weeks in mid-2010. The conceptual model included the oil reservoir and the well with a top boundary condition located at the bottom of the blowout preventer. We developed a fluid properties module (Eoil) applicable to a simple two-phase and two-component oil-gas system. The flow of oil and gas was simulated using T2Well, a coupled reservoir-wellbore flow model, along with iTOUGH2 for sensitivity analysis and uncertainty quantification. The most likely oil flow rate estimated from simulations based on the data available in early June 2010 was about 100,000 bbl/d (barrels per day) with a corresponding gas flow rate of 300 MMscf/d (million standard cubic feet per day) assuming the well was open to the reservoir over 30 m of thickness. A Monte Carlo analysis of reservoir and fluid properties provided an uncertainty distribution with a long tail extending down to 60,000 bbl/d of oil (170 MMscf/d of gas). The flow rate was most strongly sensitive to reservoir permeability. Conceptual model uncertainty was also significant, particularly with regard to the length of the well that was open to the reservoir. For fluid-entry interval length of 1.5 m, the oil flow rate was about 56,000 bbl/d. Sensitivity analyses showed that flow rate was not very sensitive to pressure-drop across the blowout preventer due to the interplay between gas exsolution and oil flow rate.

Drying sewage sludge using flue gas from power plants in China

A lot of energy is required for drying the sewage sludge produced during the wastewater treatment process in China; however, on the other hand, the thermal energy in flue gas from power plants is usually wasted as it discharges into the atmosphere. In this study, a new technique for sludge drying is introduced. The key component of the new technique is equipment of a two-stage drying and granulation that utilizes thermal energy contained in the flue gas from power plants and extends sludge contact time with flue gas during the constant-rate evaporation stage. The primary results of the implementation in the Kangshun sludge treatment plant (daily treatment capacity of 100 tons of wet sludge) show that the new drying technique is very effective economically and environmentally. The water content in the sludge was reduced from 78% to less than 30%. The resulted sludge could be used either to co-incinerate with coal in a circulating fluidized bed or to mix with clay to make better bricks. Besides the saving in the direct heating cost in the sludge drying processes by 80%, the saving in fossil fuel consumption due to reuse of the dried sludge is also significant. As a result of the implementation of the new technique in a sludge treatment plant at the scale of the Kangshun plant, about 16,440 tons of CO2 emission could also be reduced every year.

DCPT v1.0 - New particle tracker for modeling transport in dual-continuum - User's Manual

DCPT v l . O ~ New Particle Tracker for Modeling Transport in Dual-Continuum Media Users Manual Lehua Pan, Hui Hai Liu, Mark Cushey, and Gudmundu Bodvarsson LBNL April 2001 LBNL-42958 i

Reduced-Order Model for Leakage Through an Open Wellbore from the Reservoir due to Carbon Dioxide Injection

Author(s): Pan, Lehua; Oldenburg, Curtis M. | Abstract: Potential CO2 leakage through existing open wellbores is one of the most significant hazards that need to be addressed in geologic carbon sequestration (GCS) projects. In the framework of the National Risk Assessment Partnership (NRAP) which requires fast computations for uncertainty analysis, rigorous simulation of the coupled wellbore-reservoir system is not practical. We have developed a 7,200-point look-up table reduced-order model (ROM) for estimating the potential leakage rate up open wellbores in response to CO2 injection nearby. The ROM is based on coupled simulations using T2Well/ECO2H which was run repeatedly for representative conditions relevant to NRAP to create a look-up table response-surface ROM. The ROM applies to a wellbore that fully penetrates a 20-m thick reservoir that is used for CO2 storage. The radially symmetric reservoir is assumed to have initially uniform pressure, temperature, gas saturation, and brine salinity, and it is assumed these conditions are held constant at the far-field boundary (100 m away from the wellbore). In such a system, the leakage can quickly reach quasi-steady state. The ROM table can be used to estimate both the free-phase CO2 and brine leakage rates through an open well as a function of wellbore and reservoir conditions. Results show that injection-induced pressure and reservoir gas saturation play important roles in controlling leakage. Caution must be used in the application of this ROM because well leakage is formally transient and the ROM lookup table was populated using quasi-steady simulation output after 1000 time steps which may correspond to different physical times for the various parameter combinations of the coupled wellbore-reservoir system.

Well Integrity for Natural Gas Storage in Depleted Reservoirs and Aquifers

Author(s): Freifeld, Barry M.; Oldenburg, Curtis M.; Jordan, Preston; Pan, Lehua; Perfect, Scott; Morris, Joseph; White, Joshua; Bauer, Stephen; Blankenship, Douglas; Roberts, Barry; Bromhal, Grant; Glosser, Deborah; Wyatt, Douglas; Rose, Kelly | Abstract: Introduction Motivation The 2015-2016 Aliso Canyon/Porter Ranch natural gas well blowout emitted approximately 100,000 tonnes of natural gas (mostly methane, CH4) over four months. The blowout impacted thousands of nearby residents, who were displaced from their homes. The high visibility of the event has led to increased scrutiny of the safety of natural gas storage at the Aliso Canyon facility, as well as broader concern for natural gas storage integrity throughout the country. Federal Review of Well Integrity In April of 2016, the U.S. Department of Energy (DOE), in conjunction with the U.S. Department of Transportation (DOT) through the Pipeline and Hazardous Materials Safety Administration (PHMSA), announced the formation of a new Interagency Task Force on Natural Gas Storage Safety. The Task Force enlisted a group of scientists and engineers at the DOE National Laboratories to review the state of well integrity in natural gas storage in the U.S. The overarching objective of the review is to gather, analyze, catalogue, and disseminate information and findings that can lead to improved natural gas storage safety and security and thus reduce the risk of future events. The “Protecting our Infrastructure of Pipelines and Enhancing Safety Act of 2016’’ or the ‘‘PIPES Act of 2016,’’which was signed into law on June 22, 2016, created an Aliso Canyon Natural Gas Leak Task Force led by the Secretary of Energy and consisting of representatives from the DOT, Environmental Protection Agency (EPA), Department of Health and Human Services, Federal Energy Regulatory Commission (FERC), Department of Commerce and the Department of Interior. The Task Force was asked to perform an analysis of the Aliso Canyon event and make recommendations on preventing similar incidents in the future. The PIPES Act also required that DOT/PHMSA promulgate minimum safety standards for underground storage that would take effect within two years. Background on the DOE National Laboratories Well Integrity Work Group One of the primary areas that the Task Force is studying is integrity of natural gas wells at storage facilities. The DOE Office of Fossil Energy (FE) took the lead in this area and asked scientists and engineers from the National Energy Technology Laboratory (NETL), Lawrence Livermore National Laboratory (LLNL), Sandia National Laboratories (SNL), and Lawrence Berkeley National Laboratory (LBNL)) to form a Work Group to address this area. This Work Group is an expansion of the original “Lab Team” comprising scientists and engineers from SNL, LLNL, and LBNL which was formed to support the State of California’s response to the Aliso Canyon incident and operated under the Governor of California’s Aliso Canyon Emergency Order (1/6/2016). The Lab Team played a key role in advising the State of California’s Department of Conservation (DOC) in its oversight of SoCalGas during and after the incident.

Computational Methods in Water Resources: Proceedings of the XIVth International Conference on Computational Methods in Water Resources, 23–28 June 2002, Delft, The Netherlands.

S.M. HASSANIZADEH, R.J. SCHOTTING, W.G. GRAY, and G.F. PINDER (ed.) Elsevier Science, Amsterdam. 2002. Volumes 1 and 2. Hardback, 1808 pp.

WinGridder - An interactive grid generator for TOUGH - A user's manual (Version 1.0)

355.00. ISBN 0-444-50975-5. Following rapid advances during the last two decades, computer simulation has now become an irreplaceable part of our efforts to