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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 2018, our 1,183 drilling crews spudded 11,385 wells and completed 11,264 wells, registering a total footage of 25.71 million meters.

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 is used to prevent borehole deviation and lost circulation while facilitating drilling and eliminating formation damage. With the increasing scale of its application, underbalanced drilling is playing a more significant role in reservoir protection and boosting per-well production. Well Zhonggu5-H2 in the Tarim basin is located in complex formations featuring narrow pressure windows and multi-pressure systems. In drilling this well, Bohai Drilling Engineering Company used precise PCD (pressure controlled drilling) technology to realize long horizontal interval penetrating multiple fractured strata, with a total PCD footage of 1,153 meters. In addition, no mud leakage or drilling complications were reported throughout the whole process.

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.

Horizontal drilling

Horizontal drilling is used in large number of applications. With further improved capacity and application scale, horizontal drilling has become the major technology for the development of tight oil and gas and shale gas.

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. In Tarim Basin, Well Keshen-21 was completed at a depth of 8,098 meters; Sichuan Basin, Well Wutan-1 created a fresh record of 8,060 meters for risk drilling in the Sichuan-Chongqing region.

 

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