Welcome to an interview with Dr. Xianzheng Zhao, President of Dagang Oilfield, Petrochina. The Dagang Oilfield is an example of a continental shale oil reservoir that has been successfully placed into production thanks to advances in technology, reservoir modeling, and geochemical analysis.
Which Chinese petroleum provinces have you worked in?
First, I would like to say that it is an honor for me to participate in the AAPG Learn! Blog. I am happy to share the experience, technology and knowledge of oil and gas exploration and development in China. We welcome experts and scholars in international oil companies to visit China and participate in the exploration and production of hydrocarbons.
I have been long engaged in evaluation and strategic planning of exploration areas in continental petroliferous basins of China. In the recent two decades, I have focused more on the research and practice of oil and gas exploration in continental rift basin, especially on lithologic reservoir, reservoir in inner buried hill, continental shale oil in hydrocarbon-rich sag with high-mature exploration regions ，and economic exploration & exploitation for high rank coal-bed methane.
What were some of your specific studies or projects?
Currently, I am in charge of or participate in four major national science and technology projects: namely, “Study on oil and gas enrichment pattern and reserve increase domains in northern Bohai Bay Basin”, “Distribution pattern and resource evaluation of oil and gas in deep formations of petroliferous basins in China”, “Demonstration project of coalbed methane development with horizontal well in Qinshui Basin of Shanxi province”, and “Control mechanism of multi-lateral wells in coalbed methane development”.
Besides, I also take charge of four major science and technology projects of PetroChina: namely, “Study and application of key technologies for increasing and keeping 8 million tons of oil equivalent production in Huabei Oilfield”, “Study and application of key technologies for increasing reserves and keeping stable production in Dagang oil province”, “Study and application of key technologies for exploration and development of medium maturity continental shale oil”, and “Study on key exploration and development technologies for high rank coalbed methane in Qinshui Basin”.
What were a few of the petroleum system or province's characteristics?
Lithologic reservoir in trough area of rift basin: trough area refers to the secondary negative structural unit separated by uplifts inside sedimentary sag, which is the secondary depocenter in sag with big area and low exploration degree. Trough areas often have thick formations and multiple sets of source-reservoir assemblages. Moreover, they are close to oil source, often have had multi-stages of oil and gas charging and sufficient oil and gas supply from multiple sources. But reservoirs in these areas are often large in burial depth and poor in physical properties.
Primary oil pools in inner buried hill of rift basin: Paleozoic inner buried hill contains coal-bearing strata, so there develops a petroleum system with the coal measure as source rock and Mid-Paleozoic as reservoir, where medium-large primary oil and gas pools are likely to occur. But the reservoirs are poor in physical property after strong diagenesis, and it is hard to predict high-quality reservoir and implement stimulation.
Continental shale oil: Compared with marine shale in US, shale in China are mostly continental facies, new and distributed in Cenozoic and Mesozoic, with more complex structure, richer faults, poorer continuity, stronger heterogeneity and lower maturity (Ro between 0.6% and 1.2%). They consist of multiple types of rocks, mainly including felsic, mixed and limy dolomitic shale, dolomitic sandstone and doloarenite etc. Therefore, the exploration and development of shale oil in them are more difficult.
Please describe one of your favorite tools or techniques that have yielded fresh insights.
Accumulation theory and exploration technology of oil in trough area of continental rift basin: Based on 3D merged seismic data volume, the favorable structural and lithologic belts in trough area have been sorted out, accumulation models of stratigraphic-lithologic reservoir and deep inner buried hill reservoir have been figured out, reservoir prediction under constraint of facies and prediction technique for naturally fractured reservoir in buried hill have been worked out, and fast and high quality drilling technology and high efficient stimulation technology for low quality reservoir have been innovated.
Enrichment and accumulation theory of retained hydrocarbon in thick continental shale layers and sweet spot evaluation technology: We found thick continental shale layers featured “3 highs and 1 low” (high frequency lamellar structure, high quartz content, high organic matter content and low clay content), dominant fabric shale had rich micro-nano pores, with areal porosity of 11%; the shale at medium maturity (Ro 0.6%- 1.2%) had significant crossover effect and rich movable retained oil able to accumulate into oil pool, overthrowing the idea obtained from overseas marine shale oil exploration that only high maturity shale could be rich in oil. Moreover, we have sorted out crossover effect（S1*/TOC）and brittleness index etc 8 parameters to establish a quantified identification method of shale oil sweet spot in continental thick shale layer.
What are some of the new or future techniques that you may dramatically change how we explore for and produce hydrocarbons?
Shale oil exploration and development technology: Because shale oil has huge resources of over 2 times those of conventional oil and gas. But the exploration and development technologies for shale oil, including sweet spot comprehensive evaluation and volumetric fracturing etc. still need further research, once breakthroughs are made, they will change the oil and gas exploration in the future dramatically.
New energy development technology: As solar, biomass, water, wind, and tidal power and ground heat and are renewable, if breakthroughs are made in the exploitation of them, they can sustain the lasting development of human society, and replace limited fossil fuel that can pollute environment.
Please recommend a book that you think the audience may enjoy.
RE-EXPLORATION PROGRAMS FOR PETROLEUM-RICH SAGS IN RIFT BASINS