Lost circulation in fractured strata during drilling incurs additional costs and leads to difficulties in promoting drilling safety and efficiency. Plugging-while-drilling is a feasible means to address lost circulation in fractured formations. The particle size distribution (PSD) of plugging particles is determined empirically; therefore, it is often not matched with the fracture sealing requirement. This study investigates the lost circulation mechanism of fractured strata and identifies a calcite particle-based material as the preferred plugging agent. The plugging mechanism and the design of PSD and particle concentration are demonstrated. Based on the concentration, a plugging-while-drilling technique was developed for fractured strata. The results show that calcite particles tend to form the filling layer at the fracture inlet, which cuts off the leakage of the drilling fluid into the fracture, eliminating the drilling fluid pressure applied on the fracture surface. Thus, a stable sealing for the fractured formation is achieved, and the pressure-bearing capacity of the borehole wall is increased. The result also reveals the optimal mixing and concentration models for calcite particles with various diameters. The plugging technique based on calcite particles for fractured formations is applied in a field experiment. The results confirm that the technique can improve the chance of lost circulation prevention and thief-zone plugging in fractured strata and remarkably reduce both the event quantity of lost circulation and the volume of circulation loss. The findings of this research lay a theoretical basis to address lost circulation in fractured formations and, thus, have important practical significance.

钻井过程中裂缝地层的漏失会产生额外的成本，并导致难以提高钻井安全性和效率。随钻封堵是解决裂缝性地层漏失的可行方法。堵塞颗粒的粒径分布（PSD）根据经验确定；因此，它往往与裂缝密封要求不匹配。本研究调查了裂缝地层的堵漏机制，并确定了方解石颗粒材料作为首选堵漏剂。演示了堵塞机制以及PSD和颗粒浓度的设计。在此基础上，开发了裂缝性地层随钻封堵技术。结果表明，方解石颗粒倾向于在裂缝入口处形成充填层，切断了钻井液向裂缝中的泄漏，消除了施加在裂缝面上的钻井液压力。从而实现对裂缝地层的稳定密封，提高井壁的承压能力。结果还揭示了具有不同直径的方解石颗粒的最佳混合和浓度模型。基于方解石颗粒的裂缝地层封堵技术在现场试验中得到应用。结果表明，该技术可以提高裂缝性地层的防漏失漏率，显着减少漏失事件量和漏失量。这项研究的结果为解决裂缝地层中的漏失奠定了理论基础，因此，