A significant improvement in deepwater well integrity can be accomplished by deepening the structural casing to have a dual functionality. This exploits the rapid growth of formation strength in the shallow first 1,000–2,000 ft below the seafloor. This first casing string in the deepwater well design would, firstly, support the axial and bending loads of the wellhead, blow out preventers, riser, and subsequent casing strings, as is the current practice, and secondly, provide sufficient casing shoe strength to mitigate the shallow drilling hazards. The basis for this recommended well design change has been the sporadic drilling performance in the execution of deepwater drilling operations, especially for exploration and appraisal wells, which has included some significant catastrophic well failures.

The placement of the structural casing significantly deeper than current practice allows the well design to have larger casing diameters in the deeper well sections. This significantly improves deepwater well integrity by decreasing circulating friction. The current practice in the riserless section is to place casing seats above the identified shallow drilling hazards. The study reviews and evaluates the feasibility of setting the subsequent riserless casing strings according to the pore pressure and fracture gradient environment. This requires fewer casing strings to reach the planned well depths, which results in larger casing annuli across the deeper narrow pore pressure/fracture gradient (PP/FG) environment than in current deepwater well designs. This increase in annular space reduces the circulating friction across these sections, decreasing the loss of circulating/well kick cycles that are problematic and can prevent drilling from continuing to planned well depths.

This study evaluates the effect of deepening the structural casing for the improvement of well integrity. The feasibility of various drilling methods and technologies required to deepen the structural casing, including conventional drilling, jetting, casing drilling, and reaming, are reviewed and evaluated. The method proposed for this deepening is the application of casing drilling technology. Its principles and merits are reviewed as it would be applied in a subsea environment in mitigating shallow drilling hazards and facilitating the deepening of the structural casing. Finally, the value of this proposal is evaluated in terms of meeting well objectives, improving well integrity, and reducing well construction time.

通过深化结构套管使其具有双重功能，可以实现深水井完整性的显着改善。这充分利用了海底以下1,000-2,000英尺的浅层地层强度的快速增长。按照目前的做法，深水井设计中的第一根套管柱将首先支撑井口的轴向和弯曲载荷，防喷器，立管和后续的套管柱，其次，将提供足够的套管靴强度以减轻浅层钻井的危害。推荐的井设计更改的基础是深水钻井作业（尤其是勘探和评估井）执行过程中的零星钻井性能，其中包括一些重大的灾难性井故障。

结构套管的放置要比目前的做法深得多，这使得井设计在较深的井段中具有更大的套管直径。通过减少循环摩擦，这可以显着改善深水井的完整性。在无立管部分，目前的做法是将套管座放置在已确定的浅层钻探危险之上。该研究回顾并评估了根据孔隙压力和裂缝梯度环境设置后续无立管套管柱的可行性。与目前的深水井设计相比，这需要更少的套管柱才能达到计划的井深，从而在更深的窄孔隙压力/裂缝梯度（PP / FG）环境中产生更大的套管环空。环形空间的增加减少了这些部分之间的循环摩擦，

这项研究评估了加深结构套管对改善井完整性的影响。评估和评估了加深结构套管所需的各种钻井方法和技术的可行性，包括常规钻井，喷射，套管钻井和铰孔。提出的深化方法是套管钻井技术的应用。综述了其原理和优点，因为它将应用于海底环境中，以减轻浅层钻探危险并促进结构套管的加深。最后，根据实现油井目标，提高油井完整性和减少油井建设时间来评估该建议的价值。