Research and Application of LWD Geosteering Technology Based on Geophysical Inversion
Authors: Zhu Meng , Cui Yunjiang , Ma Chao , Xu Jinxiu , Yang Wei , Li Ting 
Published: April 2019

Caofeidian oilfield in Bohai Sea has the characteristics of low structural amplitude, low oil column height, complex structure and reservoir change, complex fluid system, large reserve of bottom water reservoir, and all use horizontal well development. How to accurately control the well trajectory to make the horizontal well successfully landing, improve the level of drilling encounter rate, to achieve the ideal height of water protection is the key to achieve the optimal development effect. After many years of development, the geological-oriented technology has been adopted for the drilling of the oil field, which has achieved good application results. However, with the development of the oil field, the reservoir changes facing at present are more complex, and the reservoir with lower oil column height, which is limited by the density of the offshore well net, the traditional Geological guidance technology of follow-drill logging has great limitations, and it satisfies the implementation requirements of horizontal well.

Aiming at the above problems, the seismic attributes are connected with the logging curve through the cluster analysis method, and the natural gamma and over-well seismic attributes (maximum amplitude) are innovated) the relationship between the resistivity and the natural gamma curve is established, and the pre-drilling geological guidance model is established.

This method not only gives the meaning of seismic attribute logging, it also solves the shortcomings of the traditional modeling error caused by the large horizontal difference between the design wells and the guide wells, the difference of fluid properties and the small detection of the fan enclosure. At the same time, the geological guidance technology in Caofeidian Oil Field low oil column bottom water reservoir with Drilling Technology series, improve the landing prediction accuracy and level segment well trajectory control ability. In the past three years, nearly 50 horizontal wells were implemented in Caofeidian Oilfield, and the average oil layer drilling rate of the horizontal segment reached 90, according to statistics, it has improved 10% on the drilling encounter rate before using the geological guidance technology, which is also adaptive in other oil fields, and 4 horizontal wells were drilled in the B oilfield in 2018, the gamma-ray and resistivity curves of non-drilled sand bodies above the target layer have been successfully retrieved, and the aim of accurately guiding the horizontal well landing has been achieved.

Geosteering services could improve geological reservoir development effect, decrease difficulty in drilling and completion engineering, reduce drilling cycle, and enhance economic performance of oil & gas field development. The authors believe that scientific and effective development of oil & gas fields requires all departments and professions to cooperate closely, and the cooperation could get more perfect by timely using geosteering services. Geosteering services play an important role in reservoir engineering, drilling and completion, and drilling management, etc., connecting various professions seamlessly.