Upstream activities of the petroleum industry are generally presented in categories of proved reserves and volume of crude oil and natural gas produced. This paper analyzes the upstream activities from the point of view of capital outlays. Number of wells drilled and success ratio in individual countries and continents for the period 1983-1998 is analyzed with the reference to the whole post-war period. Such the analysis is worthwhile as trends of drilling (exploration) activities are completely different from the trends of hydrocarbon proved reserves and oil and gas production. Trends of reserves and production are highly stable and world-wide trends increase, thus their econometric study may deal only with a shape of the trend (change from exponential to linear one). Drilling activity trends have, on the contrary, very strong cyclical fluctuations caused mainly by changes in crude oil prices and capital price and availability. The policy determined for the post-crises period is related in each case to the published results obtained for the previous periods. The detailed results are presented for 25 countries and regions. In Germany, Austria and France the decrease in drilling activity occurred to the never before observed level. The chaotic policy of investors has been found at average success ratio about 60% what means that new oil and gas fields were searched. Italy drilled more wells than its neighbors, with the similar success ratio. Decrease in upstream investments was observed also in the Netherlands where lower risk was taken (average success ratio 69%). A high increase in drilling expenditures occurred in countries operating on the North Sea (United Kingdom, Denmark and Norway). The investors used the opportunities - cost advantage and political events (collapse of Soviet Union and Persian Gulf War) - to strengthen their positions on oil and gas markets. The drilling activity in these countries concentrated on development of existing oil and gas fields (high success ratio) while search for new fields and long-term goals were neglected. The study of West-European exploration policy showed that upstream petroleum industry in this region "has aged" and is now similar to the exploration industry in USA and South America: shift to abnormal policy, high increase in success ratio, and low reserves to production ratio. The recession in the US upstream petroleum industry is discussed in detail. Old, low-productive and high-cost American oil and gas fields were eliminated from the market what caused the number of wells drilled annually to drop in the analyzed period from about 80 thousand to about 30 thousand, flow of capital outside USA and bankruptcy of many companies. The success ratio reached historical level of 75% and the proved reserves decreased. The new situation caused, however, the positive economic changes to occur: restructurization of the industry, mergers of companies, cutting costs, lowering employment etc. Opposite changes occurred in Canadian petroleum industry in the post-crisis period: the number of wells drilled and success ratio amounted to the never reported levels. In Mexico, the decrease in number of wells drilled and increase in success ratio were observed. Drop in drilling activity and success ratio increase occurred also in Venezuela and Brazil while in Argentina the post-crisis period has brought the highest historical level of upstream investing activity what placed the country on the third place in the free-market world - after USA and Canada - as regards number of wells drilled. African countries were not involved strongly in search of new oil and gas fields and their activity was concentrated rather on development of existing fields (average success ratio 75%). Low-cost hydrocarbon deposits enabled them to increase sales volume of oil and gas without substantial investments. Bigger changes occurred in exploration policy of Middle East countries where number of wells drilled amounted to the historical level at average success ratio of 87%. As this region produces oil at the lowest cost (2-3 dollars per barrel, while in Africa, South America, and Far East the cost is 6-7 dollars, and at least 10 dollars in Europe and USA), it was very attractive for the investors, to say nothing about low geological risk. The historical level of drilling activity was observed also in Indonesia at average success ratio of 81%. The only country highly interested in the search of new oil and gas fields and ready to take the high geological risk was Australia where the average success ratio for the post-crises period was only 51%. Intensive drilling activity was carried out also in India, Thailand and Malaysia, but their main goal was to develop existing fields. Summarizing the changes occurred in the post-crisis period, the increase in number of wells drilled was reported in oil exporting countries while number of wells decreased in countries of old oil industry and in oil importing countries. In total, the post-crisis period has brought the drop in upstream investments - the increase in number of wells drilled occurred only in 16 areas while strong decrease in 20 countries of 50 being analyzed in this paper. The total average success ratio for free-market countries was 73.5%. The substantial changes in world upstream petroleum industry that took place in post-crisis period are more evident if the period is split into two eight-year subperiods. In the first subperiod (1983-1990), 506 thousand of wells were drilled in the free-market world while in the second subperiod (1991-1998) only 335 thousand. The total average success ratio in the first subperiod was 70.9% while in the second subperiod amounted to 77.1%. The first change was caused by the shift of capital investment from upstream to down- stream activities, due to higher requirements in the field of environment protection and low profitability of drilling investments. The increase in success ratio was caused by high progress in exploration technology and by change in petroleum companies strategy. The low oil and gas prices and competitive market caused companies to abandon long-range planning of new discoveries and to start a low-cost exploitation of proved hydrocarbon reserves. The change in strategy caused that for the most of countries studied in this paper the chaotic exploration policy has been revealed and that econometric models used successfully for the previous periods are rather not significant for post-crisis period.