Limit analysis of extended reach drilling in South China Sea

Abstract

Extended reach wells (ERWs), especially horizontal extended reach well with a high HD (horizontal displacement) to TVD (true vertical depth) ratio, represent a frontier technology and challenge the drilling limitations. Oil and gas reservoir in beaches or lakes and offshore can be effectively exploited by using extended reach drilling (ERD) technology. This paper focuses on the difficult technological problems encountered during exploiting the Liuhua 11-1 oil fi eld in the South China Sea, China. Emphasis is on investigating the key subjects including prediction and control of open hole limit extension in offshore ERD, prediction of casing wear and its prevention and torque reduction, 244.5mm casing running with fl oating collars to control drag force, and steerable drilling modes. The basic concept of limit extension in ERD is presented and the prediction method for open hole limit extension is given in this paper. A set of advanced drilling mechanics and control technology has been established and its practical results are verifi ed by fi eld cases. All those efforts may be signifi cant for further investigating and practicing ERD limit theory and control technology in the future.

Overview on vertical and directional drilling technologies for the exploration and exploitation of deep petroleum resources

“…The longest well is the well Z-42 that drilled in Chayvo of Russia in 2014, its measured depth was 12,700 m, while its horizontal displacement reached 11,738 m. Currently, the horizontal displacement of most oil wells can research about 2000-4000 m. However, the difficulties of extended-reach drilling depend on not either the horizontal displacement or the vertical depth, that means it depends on the horizontal displacement to vertical depth ratio (k = HD/ VD = horizontal displacement/vertical depth). In general, k & 0 represents conventional vertical wells, 0 \ k \ 2 belongs to directional or horizontal wells, 2 \ k \ 3 belongs to conventional extended-reach wells, while k [ 3 belongs to extended-reach wells with ultra-high horizontal displacement to vertical depth ratio (Gao et al 2009). Due to the development of the directional drilling technology, the extendedreach drilling, especially horizontal extended-reach drilling with a high horizontal displacement to vertical depth ratio, represent a frontier technology and challenge the drilling limitations (Gao et al 2009).…”

“…In general, k & 0 represents conventional vertical wells, 0 \ k \ 2 belongs to directional or horizontal wells, 2 \ k \ 3 belongs to conventional extended-reach wells, while k [ 3 belongs to extended-reach wells with ultra-high horizontal displacement to vertical depth ratio (Gao et al 2009). Due to the development of the directional drilling technology, the extendedreach drilling, especially horizontal extended-reach drilling with a high horizontal displacement to vertical depth ratio, represent a frontier technology and challenge the drilling limitations (Gao et al 2009). …”

“…22,23, and these technologies has advanced from real-timized to digitized, visual, automated, integrated and intelligentized (Ma and Chen 2015). However, the challenges of directional drilling are different with the vertical deep drilling, and can be concluded as follows (Allen et al 1997;Walker et al 2009;Gao et al 2009;Walker 2012;Gupta et al 2014;Yan et al 2014;Ma et al 2015a;Liu et al 2016b):…”

The Maximum-Allowable Well Depth While Drilling of Extended-Reach Wells Targeting to Offshore Depleted Reservoirs

“…The initial concept and model for open hole extension limit of extended-reach drilling was proposed by Gao (2009) [20]. Due to the complexity of the drilled formations and borehole hydraulic conditions, then several models were updated.…”

Prediction of casing wear in extended-reach drilling

“…Therefore, it is important to predict casing wear so as to optimize the material grade and wall thickness of the casing and/or install pipe protectors for ERD operations (Gao et al, 2009). This can improve drilling safety, reduce accidents, save drilling costs, and prolong the life of oil & gas wells.…”