Peel back the flat, brown surface of the north China plain -- dry and dusty at this time of year -- and you will uncover a geologist's paradise. Steep, jagged peaks of Himalayan height drop down into deep rifts and valleys formed in the days when the earth's crust heaved and subsided as if a giant hand were crumpling or smoothing a piece of paper.
Here and there, amid these peaks and valleys, nature formed giant rock caverns -- 500, 600,800 million years old. Much, much later, perhaps as recently as 50 million years ago, rich hydrocarbons from decomposing continental vegetation seeped into these natural reservoirs. There they lay until man's restless search for energy brought oil drills sinking their jagged teeth deeper and deeper into successive layers of rock.
Suddenly, meeting no resistance, the "bit" or teeth would sink three feet or more. To the oil-rig operators watching sensitive recording instruments on the surface, this would be the sign they were waiting for: They had struck oil.
Renqiu oil field 90 miles south of Peking is little more than four years old, yet it produces more than 10 million tons of oil per year, according to Cha Qianheng, chief geologist of the north China branch of the China National Petroleum Corporation.
This oil field thus accounts for 10 percent of China's oil production (106 million tons in 1979). Wu Han, manager of the science and technology department of the same branch, thinks output can easily be doubled within the next five years. These optimistic comments were made to journalists accompanying a group of geologists and other experts from developed and developing nations attending a United Nations conference in Peking.
The geologists and the journalists were the first foreigners to visit Renqiu since the oil field's discovery in 1975. Renqiu oil, like that of Daqing in northeast China (50 million tons per year) and Shengli in neighboring Shandong province (20 million tons per year) is of the "buried hill" type. Its reservoir sits under a buried hill, as does oil in other parts of continental China, in Egypt, and in the North Sea.
The exciting thing about Renqiu, according to the visiting geologists, is that like most oil discovered in China so far, it is of the "continental" rather than the "marine" type -- it comes from land vegetation, not marine.
Whereas in the Middle East, North America, and most other places continental rocks have seldom yielded oil in commercial quantities, in China they do. Chinese geologists are understandably proud of having reversed accepted wisdom in this field.
Daqing, discovered in 1959, has passed its production peak. New oil must constantly be discovered elsewhere if oil production in China is to climb toward the 500-million-tons- per-year level that its geologists think possible within the next 20 years. Five hundred million tons per year is Saudi Arabia's present level and would make China one of the world's foremost oil producers.
Renqui, Messrs. Cha and Wu say, is one of the most promising oil fields discovered in recent years. Renqui alone produced over 10 million tons last year. Exploration, which had been concentrated in an area of 200 square kilometers, is moving northward, southward, and westward of the original strike, where new fields of as yet unannounced size are coming into production -- Ba Xian, Yong Qing, Yanling, and Hejian.
Renqiu oil has a low sulfur content (0.03 percent) and high wax content (16 to 22 percent) and is therefore similar to Daqing oil, which China exports to Japan and elsewhere. Of the nearly 100 wells sunk so far, No. 11 is one of the most productive: 2,731 meters deep, it brings up 2,000 tons per day at a temperature of 117 degrees C.
Several other wells produce 1,000 tons per day, operators on the site said. So far, none of Renqiu's oil has been exported. It is piped north to Peking and south to other industrial sites. Like Shengli and Dagang near Tianjin (4 million tons per year) one of Renqiu's great advantages is its accessibility. It is neither offshore nor in remote Qinghai or Sinjiang, but planted squarely in the middle of one of China's most populous areas.
Exploration continues in a 10,000 square kilometer area, Chinese experts said , and will eventually cover 30,000 square kilometers considered to offer the most promising possibilities. The experts emphasize that as they dig deeper they may well find new reservoirs, perhaps with older, "sweeter," lighter oil.
Meanwhile, here and there across the flat, nearly treeless plain where rows of commune members are busy hoeing their fields, an oil derrick lifts its proud head, a sentinel of progress in China's drive to catch up with the world's major industrialized nations by the end of this century.