The First Highly Deviated Well Coring in Qinghai Oilfield Was A Success

Recently, the Natural Gas and Risk Exploration Project Department of the Qinghai Oilfield Exploration Division successfully drilled and cored well Xiandong 8 in the Xiandong Fault Block Group in the Qaidam Basin. A total of 3.23 meters of oil and gas core were obtained, with a core recovery rate of 96%. Two sections of the core have good oil content, reaching oil immersion and fluorescence levels respectively, accounting for 11% and 12% of the core length. The well shows active oil and gas, confirming The oil content of the N21 formation in the east wing of the Nanbaxian fault block was determined.

Well Xiandong 8 is located on the east side of the Nanbaxian Oil and Gas Field in the Qaidam Basin. It was deployed by the oil field in order to explore the oil reservoir enrichment rules of the Xiandong Fault Block Group and further confirm the oil and gas scale and distribution rules of the Xiandong Fault Block Group. A pre-exploration well, designed as an inclined well, was drilled along the fault at a steady inclination of 45.69 degrees, and was completed at layer E32.

The formations in the Nanbaxian area have poor diagenetic properties, strong slurry-making performance, and extremely difficult wellbore cleaning. If you are not careful during the drilling of conventional vertical wells, "sticking" can easily occur, let alone the drilling construction of highly deviated wells, which can be described as "extremely difficult." Disaster". This coring work faces the possibility that a 45-degree well inclination can easily form a cuttings bed and cause coring to become stuck. At a 45-degree well inclination, the outer cylinder is straightened but the inner cylinder has coaxiality deviation and difficulty in coring, which affects the harvest rate. Coring The N21 layer is under-compacted and is prone to core blockage and core breakage. Coring of the target layer is prone to many difficulties such as stuck pipe due to the pressure difference between the formation and the wellbore.

In order to successfully realize the coring of highly deviated wells, oilfield drilling and geological professional management personnel are stationed in the well to coordinate coring-related matters and make all-round efforts to anchor the target.

Improve wellbore conditions before coring

Taking advantage of the integration of geology and engineering, in the face of problems such as many faults, high difficulty and high risks, we fully demonstrated the well structure, well trajectory, well wall stability analysis, etc., compiled a "corresponding" drilling and completion construction plan, and Develop corresponding countermeasures from aspects such as speed-up ideas and tool technology. During the drilling process, eight measures including strengthening research while drilling, optimizing wellbore trajectories, drilling parameters, and wellbore cleaning were carried out to ensure that the drilling trajectory was smooth enough, the wellbore conditions were clean enough, the drilling fluid performance was excellent enough, and the coring tools were used before coring. Be prepared enough.

Strengthen supervision of the coring process

Assign a first-level drilling engineer to supervise tool inspection and assembly on site, discuss and improve coring measures based on formation lithology, and clarify wellbore conditions, mud performance, coring parameters, operation essentials, equipment support, etc. At the same time, the geological director of the project department was stationed on site and participated in the entire coring operation, checking the core extraction and core description. Through the joint efforts of both parties, Party A and Party B finally achieved the successful coring of the 45-degree inclined well section and obtained oil and gas discoveries.

It is understood that Well Xiandong 8 was successfully drilled on October 14, and the oil layer casing cementing was completed on October 23. All constructions were carried out smoothly, and all kinds of geological data were collected and accurate. The quality of the drilling well body and the cementing quality were All met the design requirements and achieved breakthroughs in highly deviated well drilling, coring, well completion and other engineering projects, laying a solid foundation for subsequent exploration and development in the Nanbaxian area.

In the next step, the Natural Gas and Risk Exploration Project Department of the Exploration Division will carefully organize the oil testing construction of Xiandong 8 Well, speed up the progress of production and operation organization, and achieve production at an early date.