A horizontal well with the largest displacement drilled in Quaternary unconsolidated strata completed

Publish time:7/24/2007 3:04:00 AM      Source: CNPC
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On July 11, a horizontal well (Tai H5-1) drilled in Quaternary unconsolidated strata with a displacement of 1,277.47m was completed in Tuha Oilfield.

The Quaternary unconsolidated strata are characterized by loose texture, poor diagenetic property, considerable water-taking swellability and large debris dispersity, which will bring tremendous risks of leakage, blow out, collapse and bit freezing, as well as many difficulties and challenges such as applying pressure on bit and sticking-preventive lubrication during drilling.

Well Tai H5-1 is allocated on a class Ⅲ anticlinal structure in the central sag of New Sanhu depression in east Qaidam Basin, with a designed true vertical depth of 1,576.38m, slant depth of 2,734m and horizontal interval of 1,000m.

The well, spudded on May 13 and completed on July 11, is drilled by No. 40667 drilling crew of the No. 2 Drilling Company of Tuha Petroleum Exploration and Development Headquarters. Five national drilling records in Quaternary unconsolidated strata have been made by the crew, i.e. 1,009m horizontal interval, 1,277.47m horizontal displacement, maximum borehole deviation of 91.7 degree, 100% gas formation encounter rate and Φ244.5mm casing running depth of 1,723.16m.