Wearing bright orange coveralls and raking barbequed chicken, ribs and sausages over the coals. Sonny Petty greeted his poker-faced visitors in Mao caps with a warm Texas "How y'all?"

And after the delegation from the People's Republic of China had prowled over a sprawing machinery yard crowded with oil drilling equipment they sat down to Petty's barbeque, baked beans, cole slaw and French bread. "Ah, yes, we like it very much," said one, and an interpreter for another added, "Mr. Sun likes. It's good."

Mr. Sun is Sun Ching-wen, president of the Petroleum Corporation of the People's Republic of China, and he was heading a top-level delegation touring Houston to learn about the latest in oil equipment and technology, as part of his nation's effort to increase its energy supplies.

At the same time, across town. Bob O'Hara, a mechanical engineer with Beehtel, was poring over drawings to assure that his pumps will meet the specifications for a half-billion-dollar oil field project Bechtel is managing in Uthmaniyah, Saudi Arabia.

Elsewhere in town, Esso Exploration Co. a subsidiary of Exxon, was receiving its daily progress report telephoned from a drill rig floating on 3,900 feet of the North Atlantic 170 miles off Surinam, and other Esso experts were analyzing sonic profiles of the earth in a continuing search for more oil in the Far East.

That was in just one week this month. The week before, a group of Soviets were here for training in oil field equipment while six gas pipeline companies conferred repaetedly in the Tenneco Building on their efforts to buy natural gas from the Mexican government. All the while, the Houston office of Moody International was working with the Mexicans under a contract to inspect 48-inch gas transmission pipe - 130 miles of it being manufactured in nearby Baytown and 300 miles of it in far-off Japan.

Let there be no doubt: Houston is the energy capital of the world. The Soviet Union may be the world's largest petroleum producer, and the Middle East may supply much of the world with badly needed crude, but it is Houston that has acquired the greatest concentration of expertise, technology, equipment and supplies needed to find, pump and process energy.

It has become an international crossroads marketplace, a 20th Century high-technology bazaar - an energy bazaar, supplying the nation and the world with energy-related knowledge and goods. There is no other place like it.

From high-rise offices, the vendors in this bazaar traffic in geophysics, drilling, pumping, rig construction, "mud" that lubricates drill bits, pipelines, refineries and petrochemical plants. They bring each year billions of dollars in foreign exchange to the United States - and Houston.

"This is the center of the world," says Ted C. Rogers, president of National supply Co., a wholly owned subsidiary of Armco Steel that last year sold two drilling rigs to the Chinese and treated the Sun delegation to the barbeque.

"You have a lot here that tends to lean to the oilpatch," says Don. G. Wasson, president of Aramco Services, the U.S. purchasing and recruiting arm of Arabian American Oil Co. "You have a lot of people here who know what an oil well is."

Aramco Services moved here in 1974 from New York because it was doing most of its hiring and buying here. Today 1,000 people work for Aramco Services, and some come and go daily between here and Saudi Arabia, usually on a direct KLM flight with a single stop in Amsterdam. An Aramco-chartered TWA jetliner makes a weekly round trip.

All told, Aramco Services spent $300 million for services alone last year and, Wasson says as he sits in front of a red telephone with a direct line to Saudi Arabia, probably $300 million more was spent for goods.

Virtually every large oil company has either its headquarters or exploration and production offices here, leading one Department of Energy official to conclude: "More energy decisions are made in Houston than anywhere else in the world."

To Houston'sbenefit, business relations that began in oil have expanded to other ventures as Middle Eastern nations, notably Saudi Arabia, have begun spending their petrodollars on internal development - $143 billion worth in the case of the Saudis alone.

One estimate puts the value of current energy-related foreign contracts in Houston for goods and services at $7 billion, with more to come. Fluor Engineers and Constructors Inc. here has an engineering, procurement and construction management contract with Aramco in Saudi Arabia for $4 billion natural gas processing and transmission project stretching into the 1980s.

"We are an international city now, and we are dependent on international business," says J. L. Taylor, director of economic development for the Houston Chamber of Commerce. "We have to care about the health of the king of Saudi Arabia - we ought to be concerned with what the king of Saudi Arabia has for breakfast."

So crucial have American equipment and expertise become in helping other nations develop their energy supplies that a recent report by Congress's General Accounting Office said this resource could be one of several marshalled to offset the price-setting power of the Organization of Petroleum Exporting Countries.

To be sure, much of the money and power flowing into Houston can be attributed to the startling increases in oil prices since the Arab oil embargo of 1973-74. But this city's emergence traces back to 1901 when Spindletop, the vast reservoir east of here, gushed to the surface, spreading oil, gas and money across the landscape.

And while Tulsa once called itself the oil capital of the world, the oil companies and their vast array of suppliers have come here in growing numbers, drawn in part by the Gulf of Mexico with its offshore drilling. Bechtel, the major international construction firm headquartered in California, moved its refinery and chemical division here just last year, and Bechtel's Don Ferguson says. "This is where the activity is. Most of our clients were here, and we think more are going to be here."

Oil men have a herd instinct. "Elephants like to eat lunch together," as the Chamber of Commerce's Taylor put it. "The big decision gets made in passing at the Petroleum Club."

Today, more than 80,000 people are working for 84 major oil companies and engineering firms in Houston. That does not include the oil industry suppliers like Hughes Tool Co., which accounts for 45 per cent of the drilling bit sales in the non-Communist world.

But such preeminence does not mean control. Rogers of National Supply Co. notes that other nations can supply energy technology. Japan, for example, is a forthcoming stop for the Chinese delegation. Others say the Chinese delegation. Others say the United States is far ahead only in such specialized areas as deep and off-shore drilling.

"That technology being sent to the North Sea, to the North Slop (of Alaska) to the Saudis, that right now is what's making Houston," says Taylor.

Indeed, the Houston area accounts for some 40 per cent of the oil field equipment manufactured in the United States.

The result has been a peculiar crossing of capitalist and Communist paths - dollar diplomacy under the red star and lone star. It is the Chinese one week, their rivals the Soviets another week. It is Mexicans, Brazilians, Venezuelans. It is Texans and Russians killing two cases of vodka and concluding a night together with arms on each other's shoulders and meaningless sons in a babble of languages. It is Imco Services with "mud engineers all over the world," selling the drilling fluids that "make more hole," as Imco's Lou Buresh states it.

"In the oil and gas industry, it's a very small family," says Paul A. Mills, president of Moody International, a Pittsburgh firm with a Houston office. "A lot of that family lives in Houston."