Drilling and Well Construction in Lean Clearances in Northern Region of Pakistan

Abstract

Subject well is an exploratory well with a target depth of +/- 6000M, in one of the most challenging northern region of Pakistan. Well has multiple challenges with regards to drilling and well construction the least to mention are losses, borehole instability, intercalated formations, with steep dips along with a fault. Lean clearances in a five Casing Strings well construction were a requirement to isolate the problematic zones for safe drilling, this included running of longest 16" Liner for the first time in Pakistan, borehole enlargement of 14 3/4" to 16", later on running of 13 5/8" Flush x 13 3/8" coupled connection casing with narrow annular clearance, with customized Cementing Job to avoid surging. Running of 16" liner, drilling and construction of next section called for robust technical applications that includes drilling with aerated mud, running of 16" Liner with liner hanger for the first time in Pakistan, borehole enlargement while overcoming the various challenges as various formations (limestone, Sandstones, Clays) were drilled and later enlarged using hydraulic Under Reamer. Fit for purpose mud was used while drilling and further optimized to solid free for the smooth running of 13 5/8" × 13 3/8" Casing through lean clearance of 16" Liner. Casing running strategy has been devised to avoid Surge to formation at the same time ensuring it gets to bottom without any held up. The objectives of the section were met successfully. The paper will serve as a platform for other Operating companies in Pakistan to benefit from the lessons learnt and best drilling practices