CT Diagnosis of Well Trajectory and Completion Decision Guidance for SAGD Paired Horizontal Wells

The trajectory control quality is the key technology when using SAGD dual horizontal wells to produce heavy/super heavy oil. The systematic study of trajectory control, CT scanning diagnosis and completion decision has been carried out to guarantee the forming and keeping of steam chamber and enhance the drainage continuity and well-bore life so as to realize economical and effective development. In order to realize precise control of the trajectory of dual horizontal wells, the method with space rectangular target for dual horizontal wells and MGT magnetic-steering technology as its core, has been developed. The CT scanning diagnosis system of SAGD trajectory based on the medical technique has been developed to realize real-time scanning and predicting of the horizontal intervals of the paired horizontal wells. The timely warning and guidance of trajectory adjustment are available when the deviation of the relative position of the two wells from the space rectangular target occurs. After drilling, the space position relation of arbitrary cross-section along the trajectory axis is analyzed through the scanning diagnosis system, and scientific evaluation of the SAGD production is conducted using the SAGD efficiency coefficient method. If the relative position of certain intervals of the two wells is pretty near and there will be the risk of steam breakthrough, physical isolation of the intervals are recommended with casing and thermal packers. The technology has been applied in 12 well-groups in the Liaohe Oilfield, most of the dual horizontal wells have kept favorable position relations. During the injection well of Du-A well-group, due to the large formation dip, the scanning diagnosis system sent out warning signals when 2/3 of the horizontal interval had been drilled, then technicians adjusted the trajectory timely. After drilling, it was found that the distance between the two wells was less than 4m for a 4-meter interval at the 2/3 of the horizontal interval. During the design of completion strings, a blind tube is used to replace the screen in the interval. Two thermally-setting packers are designed respectively for the upper and lower end of the blind tube to realize physical isolation so as to ensure the formation of the steam chamber in the later period and guarantee favorable oil drainage. The overall production of the block has been increased by 15% compared to the wells in the earlier stage. After study, the SAGD trajectory control and completion decision technology with integral constraints of the space rectangular target, real time control of CT scanning diagnosis system and decision guidance after completion has been developed to successfully remove the potential developing troubles caused by trajectory control quality. With favorable applications in the field, the technology has become an important method to guarantee SAGD development effects.