BEIJING, Sept 12 (Reuters) - Venezuela President Nicolas Maduro has arrived in Beijing for a visit that will likely feature energy and debt repayment talks against a backdrop of China's souring relations with the West.

China, the world's largest importer of crude oil, is Venezuela's largest creditor and a major player in the country's oil and gas sector. Venezuela boasts the world's largest proven oil reserves, although years of mismanagement have led to its output sliding to a quarter of what it was 20 years ago.

Below are China's main trade, investment and lending activities in Venezuela's oil and gas sector.

OIL TRADE

Despite U.S. sanctions, China has been a key regular buyer of Venezuelan oil.

Since state major China National Petroleum Corp (CNPC) , a dominant investor and oil client of Caracas, stopped lifting Venezuelan oil in August 2019 following toughened U.S. sanctions, China has been receiving Venezuelan oil via traders who branded them as Malaysian.

Data from tanker tracker Kpler showed China bought 110 million barrels, roughly 300,000 barrels per day (bpd) of Venezuelan crude in 2022.

Vortexa, another tanker counting specialist, estimated China's Venezuelan oil imports, branded as Malaysian crude or a bitumen mix, averaged at 430,000 bpd during the first eight months of 2023.

Separately, to help repay debt owed to Beijing, China Aerospace Science and Industry Corp (CASIC), a state-owned, defence-focused conglomerate has since November 2020 been shipping Venezuelan crude to China. The shipments entered China through a customs green channel and not subject to import quota systems.

Officially, China has not reported any crude oil imports from Venezuela since September 2019.

Venezuelan crude grades, mostly heavy sour Merey and Boscan, are widely used by independent refineries in China's eastern Shandong province, where the oil has typically been labelled as diluted bitumen at customs to avoid being included in tightly controlled import quotas.

CNPC IN VENEZUELA

CNPC has been involved in the development of Venezuela's oil and gas sector for nearly three decades.

CNPC halted fresh investments in the country in 2009, focusing instead on maintaining a small number of existing projects, company officials told Reuters last week.

Below are CNPC's main activities in Venezuela according to its website:

In 1997, CNPC won contracts to take over extraction at the long-established Intercampo field in Venezuela's Lake Maracaibo and the Caracoles field in the Eastern Venezuela Basin.

In 2001, CNPC established a joint venture agreement with Venezuelan state oil company Petroleos de Venezuela SA (PDVSA) for an ultra-heavy oil development in the Orinoco Belt, which holds the world's largest heavy oil reserves.

This cooperation was expanded in 2006 to develop the Zumano field - which lies close to the Orinoco Belt - and to include extra heavy oil upgrading facilities producing exportable crude in 2007.

CNPC currently holds a 40% stake in the joint venture, now called Petrolera Sinovensa, which operates a number of blocks in the Orinoco Belt.

CNPC has not entered any new oil projects in Venezuela since 2009, when it committed to invest in the Junin 4 block of the Orinoco Belt, a senior company official told Reuters.

LOANS-FOR-OIL

The development of Venezuelan oil assets has been financed by Chinese state-owned banks under loan-for-oil deals.

Starting in 2007, former Venezuela President Hugo Chavez agreed to $50 billion in credit lines and loan-for-oil deals with China.

A rout in oil prices and declining output from Venezuelan fields meant that Caracas was forced to ask for grace periods on debt owed to China in 2016.

Venezuelan crude output fell to 716,000 bpd in 2022, a fraction of the 2.8 million bpd it produced ten years earlier, according to official data reported by the country to OPEC.

The cash-strapped Maduro administration again had to negotiate grace periods for some $19 billion of debt owed to Chinese banks in August 2020.

Venezuela currently owes over $10 billion to China, according to independent data.

(Reporting by Andrew Hayley in Beijing, Marianna Parraga in Houston and Aizhu Chen in Singapore; Editing by Tom Hogue)