The ocean economy has become the focus of the world since the 21st century, and offshore oil and gas have become important strategic energy due to the depletion of onshore energy. Many countries conducted various research to accelerate the development and utilization of offshore resources. The development of the offshore oil and gas industry has undergone a long period and experienced a leaping breakthrough from coast to shallow water and deep-water. In addition, the production of offshore oil and gas has increased greatly. In this paper, the development history of the offshore oil and gas industry is reviewed in terms of time, water depth, and production. Then, the development of offshore oil and gas exploitation technology and relevant equipment is demonstrated. After that, the challenges of offshore oil and gas development are indicated. Finally, the overall development trend of the oil and gas industry is summarized that deep water, intellectualization, and gas hydrates are the future focuses. The work of this paper has a certain value for people to understand the development history and the prospect of the offshore oil and gas industry.
Unconventional oil and gas in China have developed rapidly in the past 40 years. Currently, China has become the third-largest shale gas producer in the world, with an annual production of 200×10^8 m^3 in the year 2020. With the breakthrough of exploration and exploitation of coalbed methane from medium-high rank coal, the annual production in China reached 59×10^8 m^3 in 2019. Tight sandstone gas is widely distributed in West and North China, and its successful exploitation has promoted the Ordos basin to become the largest oil and gas equivalent producer in China. Under the policy support of green exploration and exploitation, unconventional oil and gas resources, such as shale oil, tight oil, hydrate, and water-dissolved gas, are also booming and making remarkable achievements. The advanced theory, economic technology, and effective scheme will bring the exploration and exploitation of unconventional oil and gas in China into a new period.
Determining the gas stored in shale is critical for the evaluation of gas in place and the selection of resource potential areas. The application of USBM (US Bureau of Mines) desorption experiment is the most common method, which adopts the buoyancy principle for measuring shale gas content. Shale reservoirs are tight with strong heterogeneity and diverse curve patterns of measured desorption data and the square root of time. Due to the limitation of testing principles and equipment, the precision and accuracy of USBM measurement can not satisfy the demand for shale gas exploration and development. Here we report the development of a new method to measure the amount of desorbed gas in shales with high resolution. The device adopts the capillary pressure principle instead of buoyancy and mainly includes a sealed tank, gas collecting cylinder, and experiment box. Lost gas is an important part of shale gas content，which is unavoidable in the process of drilling coring. Lost gas content can be estimated by field desorption results. This practical tool provides some insights into the assessment of shale heterogeneities and the prediction of sweet spots.
With the continued development of the Chinese economy, trade in food and agricultural products has increased and China is now a net importer. This paper first describes the current state of China's food and agricultural trade, and then shows that the country has reached a trade turning point. Next, the factors for the change are discussed from four viewpoints. (1) Changes in population structure, (2) national income levels, (3) prices of China's major agricultural products, and (4) constraints on land and water resources. In the future, it is necessary to establish a sound inspection system and food cold chain to prevent food safety import risks.
Tight oil is abundant worldwide, including in China, and has high development potential, and is an important source of energy for the replacement of conventional oil resources. However, tight oil reservoirs have unique resource formation, resource characteristics, and accumulation conditions that are different from conventional oil and gas resources. The key to the successful development of tight oil is the generating conditions and reservoir conditions of tight oil reservoir conditions. In this paper, based on previous studies in China, the geological characteristics and enrichment characteristics of tight oil reservoirs are systematically summarized from the generating conditions and reservoir conditions, and the value range of evaluation indexes for the sweet core area of tight oil in China is defined. This paper has a certain reference value for the formation and distribution of tight oil and resource potential evaluation.
Reevaluations of original oil well data are an effective method for fine reservoir evaluation. In this study, two methods of generation conditions and hydrocarbon expulsion characteristics are used to reevaluate the data of five original oil wells in Shahejie Formation Lower Third Sub-member (Lower Es3) and Upper Fourth Sub-member (Upper Es4) of Jiyang depression, Shahejie Formation, Bohai Bay Basin. The results showed that: (1) Lower Es3 of Zhanhua sag and Dongying sag have certain shale oil development potential, however, the overall evaluation of hydrocarbon generation potential is not very high; (2) in Zhanhua sag, the hydrocarbon expulsion peak appears in Lower Es3, while in Dongying sag, the hydrocarbon expulsion peak occurs in Upper Es4; and (3) among the five oil wells, the hydrocarbon expulsion peak of Y187 Well overlaps with the positive value of hydrocarbon generation potential evaluation, and the reservoir thickness in the enrichment area is relatively large, which has a good development effect. The evaluation results are consistent with the actual development situation, which makes up for the weakness of previous shale oil reservoir research in this area, and has a certain reference value for shale oil reservoir cognition.