Application of a Unique Loss Circulation Curing Cement Spacer During Cement Placement in Geothermal Wells

Abstract

As with oil and gas wells, maintaining well integrity is critical in geothermal applications. Typically, wellbore stability is achieved by replacing the drilling fluid in the annulus with cement, thereby providing effective zonal isolation. Achieving effective zonal isolation usually requires pumping a spacer system to replace the mud prior to the introduction of cement to the annulus. It is imperative that the spacer generate sufficient downhole force to overcome the yield stress of the mud, enabling it to be successfully displaced. Prior to cementing, the mud in the well is conditioned through circulation to ensure it maintains a uniform rheological profile in and out of the well to more easily enable displacement with the spacer. However, downhole losses occasionally prohibit circulation. While lost circulation material (LCM) is commonly used to cure losses encountered prior to cementing, the severity may be such that remediation with LCM is ineffective. Thus, proper mud conditioning could then further break down of the formation, leading to even more severe losses. This paper details the unique nature of a uniquely engineered wellbore shielding (WBS) spacer, which has demonstrated its capacity to cure losses with a mechanism that delivers a sealing effect in permeable and fractured formations. The authors will describe in a case study how the spacer has been used in remediating moderate to total losses experienced in both a low fracture gradient formation and an induced fractured geothermal well in Kenya.