Integrated Application of LWD Electrical Images to Drilling, Geosteering and Real-Time Formation Evaluation: A Case Study From the Precambrian Dengying Formation, Central Sichuan Basin of China

Abstract

Abstract

Logging-while-drilling (LWD) electrical image tool combined with rotary steerable system (RSS) was used to drill a horizontal well in the Precambrian Dengying Formation, Central Sichuan Basin, China. Drilling the horizontal well was as an experiment to increase gas production from single well in the complex heterogeneous carbonate formation. Usually vertical wells were drilled to develop the carbonate gas reservoirs in the field. Drilling horizontal well in the formation, however, presents various challenges, including a large amount of mud loss caused by natural fracture and dissolution cave, low drilling rate of penetration (ROP) due to hard and abrasive rock in tight carbonate formation with low porosity, wellbore instability, and inadvertent sidetracks in deep landing target zone. There is also a high risk of gas influx events and measurement while drilling (MWD) failure due to high temperatures and mud plugging materials.

The LWD electrical images while drilling in the horizontal well revealed the depth of mud loss and low ROP, presented the abnormal geological structure dips that could cause inadvertent sidetracks, and identified the borehole breakout on borehole wall to further analyze wellbore instability while drilling. As a result of processing the electrical images while drilling, effective geosteering was performed in the horizontal section of 610 meters, of which about 216 meters were associated with dissolution vugs—possibly carbonate gas reservoir storages. The drilling events that occurred in the horizontal section included 14 bit replacements due to roller bit wear from hard and abrasive rock, 7 MWD replacements due to MWD failure at temperatures greater than 149 degC and plugging materials, and 1 key drilling directional control discussion because of abnormal geological structure dips.

This case study demonstrates an integrated application of LWD electrical images to drilling, geosteering, and real-time formation evaluation in horizontal well, and presents the significance and value of LWD electrical images when developing a horizontal well in the Precambrian Dengying carbonate formation.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016