During the field-development life of a mature extended-reach drill (ERD) project, a wide range of drilling tools and practices were introduced to continuously improve drilling performance and well delivery times. One of the main challenges encountered in the ERD wells was in the 12¼-in. curve section, and drilling through interbedded hard layers with severe downhole stick/slip and downhole vibrations. Historically, both motor and motorized rotary steerable system (MRSS) bottomhole assemblies (BHAs) were used to drill this section. However, the motor BHA's lower rate of penetration (ROP) and weight transfer problem cause it to be an economically inefficient strategy in contrast with the MRSS BHA, successfully drilled through all of the challenges with higher ROP and a relatively lower overall cost. Driven by cost reduction necessity, an intensive engineering effort was implemented by the operator and service provider drilling engineering teams to change the motor BHA into a cost-effective drilling strategy for the challenging 12¼-in section. Analyzing the design and performance of all previous motor BHAs led to identifying the main challenges. Detailed modeling was then performed, involving well trajectory design, BHA design optimization, hydraulics modeling, and torque and drag modeling. The modeling included static simulation as well as drillstring vibrations using finite element analysis (FEA) dynamic simulation. This extended engineering analysis improved the bit and BHA selection capability. Several drill bits and BHA options were modeled and simulated under different drilling conditions to determine the most stable configuration. Simultaneously through the dynamics simulation, a stable drilling parameters plan was generated to improve the drilling performance. The modeling results indicated that the lighter BHA configuration minimized BHA - formation contact area, allowing for smoother and efficient weight transfer downhole. A reduction in BHA vibration produced a step improvement in ROP and drilling performance. The engineering modeling results were implemented by replacing the previously used motor BHA drill collars with heavy-weight drillpipe and smaller size jars. This hardware change resulted in an unprecedented cost reduction, a 52% improvement over the previous motor BHA in delivering the challenging section, achieving multiple additional records, and 56% ROP improvement over the field. This paper will present the design process and the detailed results for each run. Recommendations will be provided on how this process can be applied to increase ROP performance and reduce the cost per foot for such drilling applications.
Typical well surveys are made once per stand, producing a 95-ft survey database; however, numerous things can take place in that 95 ft of pipe. Small changes in continuous inclination and azimuth lay hidden between traditional static survey stations. Processing these real-time measurements, in combination with traditional surveys, generates a definitive 10-ft survey list, resulting in an enhanced geometrical representation of the wellbore position. This enhanced wellbore positioning becomes increasingly significant in areas with high-anticollision risk. This type of survey processing was implemented in extended-reach drilling (ERD) projects in the Middle East. A comparison between the 95-ft surveys and the processed high-resolution surveys showed changes to 10 ft in the true vertical depth (TVD) measurements. Such shift in the TVD is important because it can result in having to revise planned trajectories to further minimize anticollision risk arising from the nearby TVD proximity with offset wells. This paper will present data to quantify the enhancement in TVD positioning using advanced survey processing in ERD projects in the Middle East, and its impact on minimizing anticollision risk.
Khafji Joint Operations (KJO) is operating a key oil-producing field. This field has been developed extensively via horizontal drilling technologies for the past two decades. With excessive time and costs required for new offshore structure installation, the utilizing of the existing wells to drill re-entry horizontal wells became imperative and economical solution for further field developing, while minimizing the cost per foot required for well delivery. Horizontal Re-entry operation in KJO has always been deemed totally undoable due to the fact that the 7 inch production liner in most of the old wells was tied back and cemented to surface. Hence, re-entry sidetrack operation would not have enough conventional casing strings options to allow the drill ahead to reservoir while having enough mechanical barriers to isolate the unstable shale zones. Also, slimming down the well design could not be a favored option as it does not accommodate the geo-steering, formation evaluation and completion requirements; which are essential for placing and producing the re-entry wells within KJO reservoirs. To enable these re-entry wells, the Khafji drilling teams have performed a comprehensive study and risk assessment to re-define the strategy for drilling these horizontal re-entry wells. The new strategy divided the targeted re-entry wells into three main categories based on the challenges and complexity underlying each well. Each category was then assigned key enabling technologies in mud, drilling systems, optimum drilling practices, and completion techniques. These strategies along with enabling technologies were successfully implemented in a new horizontal re-entry campaign in KJO and have managed to deliver eight of these challenging wells during years 2013 and 2014.
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