Our Experts


Geoenergis assists companies and government in identifying the available options and factors to be considered during planning and develop the best solutions in the decision-making process. The independent consultancy were conducted by experts with strong scientific and academic credential, combined with vast project experiences in the energy sector.

Our Consultants come from various backgrounds and expertise, with various level of experience.


Dr. John O'Sullivan

Geothermal Reservoir Expert

Dr John O’Sullivan is Professor Mike O’Sullivan’s son and is also a lecturer at the Geothermal Institute, University of Auckland. John continued his legacy from his father to become an expert in the field of geothermal reservoir engineering and is one of the best geothermal reservoir modellers in the world today.

John’s key skills are geothermal reservoir engineering and modelling, computational fluid dynamics, inverse modelling, and uncertainty quantification. John also has a dedicated team in Auckland that specialises in developing cutting-edge tools in geothermal reservoir modelling. Several tools in development are AUTOUGH2 (a University of Auckland TOUGH2 based simulator) and Waiwera (a new super-fast reservoir simulator), TIM (graphical user interface or GUI of TOUGH2), and a transient wellbore simulator.

Professor Mike O'Sullivan

Geothermal Reservoir Expert

Prof. Mike O’Sullivan is a globally renowned expert in geothermal reservoir engineering. He is one of the pioneers who developed the first concepts of geothermal reservoir engineering.

His research interests include modelling of geothermal fields, but more generally reservoir physics, environmental fluid dynamics, and computational fluid dynamics problems. He has pioneered computer techniques for numerical modelling of geothermal reservoir and applied them to the behaviour of many real systems. He teaches in the Postgraduate Certificate course in Geothermal Energy Technology.

Dr. Dewi Gentana

Sr. Geologist

Dr Dewi Gentana has over 38 years of extensive experience in geothermal projects. Dr Dewi Gentana stands as a seasoned expert in the field of geothermal energy. Her career spans the full stages of geothermal energy development, from initial field exploration to business development. Her robust invaluable knowledge make her a pivotal figure in the geothermal energy industry, specifically in Indonesia.

Currently, Dr Dewi actively works as a consultant geologist and lecturer at Universitas Padjadjaran. In her consulting role, she conducts reviews of pre-feasibility studies,  performs technical due diligence, and other consulting services for several geothermal projects, contributing her valuable insights to the work.

Professor Adi Susilo

Sr. Geophysicist

Professor Adi Susilo is a lecturer and senior geophysicist from Universitas Brawijaya who has more than 30 years of experience in Oil & Gas and Geothermal exploration projects. He is the former dean of FMIPA from Universitas Brawijaya for 2016 – 2020; he is still active as chairman of the centre for geological studies and disaster mitigation, Universitas Brawijaya.

His key skills include geophysical surveys, including Magnetotellurics, Resistivity, Microseismic, Gravity, Magnetic, Seismic, raw data processing, and 3D data interpretation. Currently, he is working on making a UKL-UPL document for Arjuno-Welirang geothermal field, owned by PT Geo Dipa Energy.

Sam Abraham

Drilling & Project Advisor

Sam is a senior drilling engineer with 30 years’ experience on 12 countries and over 20 geothermal fields. He is specialized in project management, drilling management, rig supervision, drilling engineering, well workovers and problem well diagnosis.

His professional experience is supported by formal education background in Master of Science (MSc) of Petroleum Technology (Applied) from Pune University, India and MSc in Engineering Management from National University, CA. He is a member of Geothermal Resources Council and the International Geothermal Energy Association. Sam is also actively published papers as a SME on geothermal drilling, engineering & project management topics with hands on experience.

Prof. Agung Harijoko

Sr. Geochemist

Agung Harijoko is a geologist who has been working 25 (twenty-five) years’ experience in energy industry with a half of the journey, 12 years involved in geothermal industry.

His experience in geothermal industry proved by the years of experience start from 2008 as Senior Geologist for Survey Argopuro Geothermal Area until 2019 he involved in Pre-Feasibility Study on WKP Gn. Ungaran. Now, he works as Head of Department Geological Engineering in Gadjah Mada University.

He has strong educational background in geosciences study (geology, geochemistry, and geophysics), apart from being Senior Geologist or Project Leader, in 2001 – 2018 he also active in publishing paper about geochemical, hydrothermal, geoscience study, and another topic. His key skill is, project management, geological mapping, geothermal geologist, and Geochemist.


Rony Prianto Nugraha

CEO – Sr. Reservoir Engineer & Modeler

Rony P. Nugraha is the CEO of Geoenergis and is currently working on his doctoral program in geothermal reservoir engineering at the University of Auckland. Rony started his career as a drilling fluid engineer for 4 years and has been involved in several geothermal drilling exploration projects during that time.

After finishing his Master’s degree from the University of Auckland, he became a drilling engineer and mud specialist, he was also working as a reservoir engineer and modeler for the Geothermal Institute, University of Auckland. His key skills are geothermal reservoir engineering and modeling, geothermal exploration and development drilling, drilling fluids, and geothermal project management.

Vicky Rai Chandra

Sr. Geologist

Vicky Chandra is a seasoned geothermal geologist with over 10 years of experience across more than 10 geothermal fields, primarily focused on advancing geothermal energy initiatives in Indonesia and, more recently, the Middle East. He holds a Bachelor Degree in Geological Engineering from Universitas Gadjah Mada, Indonesia. 

His expertise encompasses geology exploration, 3D geological modeling, resource characterization, well targeting, well prognostication, and well siting. Additionally, he extends his skills to energy modeling and the installation of ground-source heat pumps for heating and cooling applications.

Scott William Herman

Sr. Geologist

Scott W. Herman is a Geologist/Geochemist who has been working professionally in international companies and involved in many overseas projects. He has more than 12 years of geothermal experiences and have worked for several big names such as: Jacobs, Mercury, GeothermEx, Rio Tinto, Vulcan Geoscience and SYR Geociencia.

He started his journey just after he graduated from Wesleyan University U.S (1998) and started being a professional Geologist. He continued his study in University of California (2013) for a master’s degree in Geological Science.

Daniel W. Adityatama

Drilling Engineer

Daniel is professional Geothermal Project Engineer and Drilling Engineer 11+ years of diverse experience in the geothermal industries. After graduate from the Master of Energy program from the University of Auckland, Daniel continuously enriches his project management and engineering skills through active involvement in research. 

His technical acumen in geothermal reservoir resource assessment, drilling, completion, and workover operations. With a robust portfolio comprising over 28+ geothermal projects across 10+ different fields in Indonesia, Daniel has demonstrated his capability in both exploration and development phases. 

Muhammad Ghassan J. Shalihin

Sr. Geologist – Geomodeler

Ghassan is a geothermal geologist with over 7 years of experience in the geothermal industry. He holds an Master degree from Universitas Gadjah Mada and a Bachelor’s degree from Universitas Padjadjaran, both in Geology. His academic focus was on subsurface geology and hydrothermal alteration in geothermal systems.

Throughout his career, Ghassan has provided consulting and technical services for numerous geothermal fields across Indonesia, including Sumani, Way Selabung, Candradimuka, Dieng, Candi Umbul-Telomoyo, Patuha, Sembalun, IjenKamojang, KarahaTalaga Bodas, Lumut Balai, Bukit Daun, Sungai Penuh, Lahendong, and Sorik Marapi.

Astri Indra Mustika

Remote Sensing Specialist

Astri is a geoscientist and also a remote sensing expert. During her master’s study at Universitas Gadjah Mada (UGM), she joined The Geothermal Capacity Building Program  Indonesia-Netherlands (GEOCAP) as a graduate researcher focusing on remote sensing in geothermal areas.

Astri is an expert in processing various types of satellite imagery and digital elevation models by operating Google Earth Engine, ArcGIS, and Google Mapper to analyze lineament density, surface kinetic temperature, surface alteration, and prospect geothermal areas. She has been involved in geothermal exploration and development projects for more than 8 years in several geothermal fields in Indonesia.


M. Rizqi Al Asy'ari

Drilling and Workover Engineer

Rizqi Al Asy’ari is a Drilling & Workover Engineer with over 3 years of experience in the geothermal industries. He holds a bachelor’s degree in Petroleum Engineering from UPN “Veteran” Yogyakarta. 

Al Asy’ari has involved pivotal role in over 21+ diverse projects across 9+ geothermal fields, demonstrating his versatility and expertise from early exploration to post-development phases. Al Asy’ari’s approach combines thorough technical knowledge with a keen sense for practical problem-solving, making him instrumental in optimizing operations and enhancing project outcomes. His expertise showcasing a robust understanding of both technical and on-technical aspects of energy projects. 

Vincentius Adven Brilian​

Reservoir and Production Engineer

Adven is a geothermal reservoir and production engineer with more than 2 years of project experience in several geothermal fields, such as Ulubelu, Hululais, Dieng, Patuha, Sorik Marapi, Oka Ile Ange, Ulumbu, and Mataloko. He holds an undergraduate degree in Mechanical Engineering from Universitas Gadjah Mada.

Adven is skilled in geothermal resource assessment, well-testing analyses, production and injection strategy, as well as steamfield and power plant development strategy. He is also capable of conducting thermal-hydraulic modeling of geothermal reservoirs and wells using commercial softwares, such as TOUGH2, WellSim, and COMSOL Multiphysics. 

Nadya Erichatama

Project Financial Analyst

Nadya Erichatama is a Project Financial Specialist with over 3 years of experience in the geothermal industry. She holds a bachelor’s degree in Petroleum Engineering from Institut Teknologi Bandung, provided her with a strong foundation in technical knowledge and analytical skills. 

She has been involved in 7 geothermal field projects in Indonesia by analyzing project costs, financial model, and financial analysis that support strategic decision-making. Her expertise in financial analysis and geothermal development projects, demonstrates her robust understanding of both the technical and financial aspects of geothermal development. 

Triwening Larasati

Geologist – Geomodeler

Laras is a geologist with a Bachelor degree in Geology from Universitas Indonesia and 3 years of experience in the geothermal energy sector. She has been instrumental in developing several prominent geothermal projects, including Sembalun, Kamojang, Karaha-Bodas, Bukit Daun, and Sungai Penuh

Additionally, Laras’s proficiency extends to advanced geomodelling, where she has successfully executed 3D geological modeling using Leapfrog Geothermal software for several fields, including Sembalun, Sokoria, Bora Pulu, etc. She combined geoscience background and 3D modeling expertise make her a valuable asset in geothermal industry, ensuring precise and efficient resource development.

Galih Bayu Permadi


Galih Bayu is a knowledgeable and passionate geothermal geochemist with a Bachelor’s degree in Geological Engineering from Universitas Pertamina, his focus is on geothermal systems and hydrogeochemical modeling of geothermal fields. His analytical skills enable him to understand subsurface processes based on the characteristics of water and gas fluids obtained from exploration and drilling data.

Over 3 years, Bayu has been deeply involved in various studies and projects in geothermal fields such as Ulumbu, Sokoria, Tampomas, Sembalun, Jaboi, and Kamojang. He is also researching the geochemical characteristics of fluids in non-volcanic systems in Eastern Indonesia, such as Bora-Pulu, and prospective fields in the Middle East. 

Serina Andiani Pongtuluran​


Serina is a geophysicist who earned a bachelor’s degree in Geophysical Engineering from Universitas Pertamina. She focuses on magnetotelluric and gravity processing for geothermal project activities. She is proficient in geophysics software tools such as Geotools, Res2DInv, Surfer, and Oasis Montaj.

Over the past 2 years, she has been actively involved in multiple geothermal projects, including Lahendong, Candi Umbul Telomoyo, North Patuha, Bukit Daun, Sungai Penuh, and Sorik Marapi. She also has experience in geophysical data acquisition, specifically gravity, magnetic, geoelectric, and passive seismic. Her ability to integrate geophysics applications to characterize geothermal resources.


Geoenergis assists companies and government in identifying the available options and factors to be considered during planning and develop the best solutions in the decision-making process. The independent consultancy were conducted by experts with strong scientific and academic credential, combined with vast project experiences in the energy sector.

Our Consultants come from various backgrounds and expertise, with various level of experience.