Well Drilling

CNPC has a well-established drilling engineering & technical service system comprising five specialized companies engaged in drilling services and capable of providing drilling services for customer from home and abroad under various geographic, climatic and geological conditions.

We have gained substantial experiences in the drilling of ultra-deep wells, horizontal wells, directional wells, underbalanced wells, non-conventional wells and special reservoirs. A series of underbalanced drilling techniques involving different medium such as air, nitrogen or natural gas are available.

In 2010, our 1,000 drilling rigs spudded 13,121 wells, with total footage of 25.20 million meters, 1.65% more than in 2009. The domestic footage increased by 4.1% to 22.97 million meters. Our overall drilling speed saw a 5% increase, with up to a 10% increase in deep wells, thanks to the promotion of proven technologies such as optimal selection of bits and parameters and quality drilling fluid. Drilling efficiency was further improved, with the average construction cycle shortened by 5.08% to 17.92 days. We aggressively expanded our presence in the international drilling market in 2010. We entered the Iraqi drilling market by winning a drilling and directional drilling service contract for Halfaya Oilfield. We also won contracts for drilling or integrated oilfield services of drilling, mud, well logging, cementing, and mud logging for national oil companies of Uzbekistan, Kazakhstan, Korea, and Norway. Moreover, we were awarded drilling and workover contracts by Chevron and other international oil companies.

Sub-salt drilling

The sub-salt reservoir at Kenkiyak, Kazakhstan is known for its great depth, high pressure and complicated stratigraphic section. Lost circulation, blowout and sticking of drill tools were common during the drilling process, all contributing to a low drilling success ratio and presenting prominent technical difficulties.

Given the circumstances, CNPC used zwitterionic polysulfonate saturated salt-water as the drilling fluid to inhibit halite dissolution while preventing the destabilization and collapse of strata by adding anti-collapse and anti-sticking chemical agents. As a result, the 3,000-meter gas-bearing halite layer was penetrated smoothly.

Air drilling

Located in southern Iran, South Pars Gas Field is characterized by complex stratal configuration, formation fractures and well-developed pores, which had resulted in serious mud loss at most well intervals when drilling with conventional mud.

CNPC solved the problems of lost circulation, blowout, sticking of drill tools and borehole shrinkage by using air drilling and air-foam drilling while reducing the drilling cycle from 230 days to 80 days and less by optimizing drilling parameters and improving drilling fluid formulas.

Underbalanced drilling

Underbalanced drilling was used to prevent borehole deviation and lost circulation while facilitating drilling and eliminating formation damage. In 2010, 305 UBD wells were drilled, 27.1% more than in 2009.

Moxi Gas Field in Central Sichuan features low-permeability and leaky reservoirs requiring long drilling cycles. Taking advantage of the underbalanced drilling method, CNPC used high-efficiency drilling bits to boost the drilling speed by 3 to 6 times and reduce the drilling cycle from 5 or 6 months to 50 or 60 days, while avoiding formation damage and lost circulation.

A nitrogen UBD horizontal well in the Southwest Oil & Gas Field saw an 90% oil formation encountering rate, and has directly produced 56,300 cubic meters of natural gas, four to six times as much as each adjacent vertical well prior to reservoir reconstruction.

Horizontal drilling

Horizontal drilling is used in large number of applications. In 2010, CNPC completed 709 horizontal wells at home and abroad provided technical services to 158 horizontal well, much more than in 2009. Horizontal well and open-hole staged fracturing have become the mainstream technologies to enable efficient development in low-permeability gas fields.

Well Jing 52-H1Z, the first 20-lateral horizontal well in China, was completed in Damintun Sag of Liaohe Basin in May 2008, at a depth of 4,244 meters. Total footage of the well is 7,587 meters and the total horizontal reach of the main wellbore is 1,800 meters. It is a fishbone-type multilateral well drilled in the condensate reservoir of buried hill structure with the largest number of branches and largest horizontal footage in China.

Well Zhuanghai 8Nm-H3 and Well Zhuanghai 8Es-H5 drilled by CNPC in Dagang Oilfield, reached an H/V (Horizontal/Vertical) ratio of 3.92, and a horizontal reach of 4,842 meters respectively.

In Sudan’s Block 3/7, we completed two horizontal wells in 2009 by using sophisticated IGD technology. Daily output from each of the wells was consistently 2.5 times greater than that from vertical wells.

Horizontal wells completed in Sulige saw the average along-hole depth increased by 113 meters to 4,493 meters, average horizontal interval increased by 136 meters to 943 meters, and average drilling period shortened by 7 days to 71 days, as compared to those in 2009.

Ultra-deep wells

Well Moshen-1, Fenshui-1 and Lundong-1 drilled by CNPC in onshore China all have a completion depth or depth of drilling over 7,000 meters.

Well Moshen-1: Located in the Junggar Basin with a designed well depth of 7,380 meters, the drilling began in August 2006. A CNPC-made 9,000-meter rig and matching top drive system were used together with high-density and high temperature resistant KDF water-based drilling fluid system and PDC drilling bits. The well was completed at a depth of 7,500 meters in July 2008.

Well Fenshui-1: Located in the Huangjinkou structural belt in Sichuan Basin with a designed well depth of 6,500 meters, the well was spudded in July 2006. Nitrogen drilling was used in combination with a top drive system. The well was completed at a depth of 7,353.84 meters in September 2007.

Well Lundong-1: Located in the east ramp region of Lunnan area in the Tarim Basin with a designed depth of 7,650 meters, drilling began in April 2007 and ended in December, with a drilling cycle of 253 days and a completed depth of 7,620 meters.

Geothermal Power Generation in Kenya

The government of Kenya developed a new power development plan to help hydroelectric plants meet domestic electricity demand in the dry season. It expects to convert the rich geothermal resource available in the country into electricity, thereby enabling the state grid to serve 90% of the country’s population by 2030 and increasing the percentage of electric consumption in rural and mountainous regions.

In 2006, CNPC Great Wall Drilling Company (GWDC) won a drilling contract for the geothermal power generation in Kenya, which would add 70MW generating capacity to the country. In 2007-2008, GWDC concluded a contract for the drilling of additional 25 geothermal wells in Kenya. The average daily output of steam per single well is 5 MW. Especially, well OW909 achieved a daily testing rate of 12MW, which is now the No.1 high-yield geothermal well in Africa. In 2010, GWDC worked with China Import and Export Bank to financially and technically help Kenya promote the exploitation and utilization of geothermal resources under a framework agreement in the field of energy cooperation between the governments of China and Kenya. The company will provide comprehensive drilling services for 26 geothermal wells in the OLKaria 4 Block, 140 kilometers west of the capital city Nairobi.

Firefighting in Turkmenistan

On October 28, 2006, an enormous blowout and fire occurred at well Osman-3 in the Amu-Darya basin, Turkmenistan. Upon Turkmenistan's request for help in early November, CNPC immediately sent an experienced firefighting crew.

Despite the fact that the hydrogen sulfide level was as dangerously high at 34.5 g/m3 and there was no adequate logistical support in the desert, CNPC's firefighting crew used unconventional methods and successfully controlled the blowout and put out the fire by removing the damaged wellhead and installing a new wellhead. In February 2007, the difficult rescue and firefighting operation at well Osman-3 was completed in close cooperation with Turkmenistan and US rescue teams.