Analyzing and Understanding the Underground Blowout

Abstract

Grace, R.D., Grace, Shursen, Moore & Assocs. Inc. IADC and SPE Member Abstract The underground blowout can be the most difficult, dangerous, and destructive situation in well control. If the blowout is shallow, cratering can result and endanger the lives of all involved. The underground blowout is often denied since the usual manifestations of a blowout is hidden from view. It is imperative that the blowout be recognized and diagnosed as soon as possible. This paper examines actual case histories of numerous underground blowouts. The techniques used to understand the blowouts are presented. Specifically, analyses of surface pressures, temperature surveys, and noise logs on these specific blowouts are presented and discussed. The paper illustrates how the analyses of surface pressure data and temperature surveys are very definitive in understanding the underground blowout. In the cases studied, the noise log interpretation is shown to be confusing and inconsistent. Introduction Underground blowouts are generally more challenging than surface blowouts. The volume of influx is not known nor is the composition. Further, the condition of the well bore and tubulars which are involved are not reliably descriptive. The well control specialist is confronted with the necessity of analyzing and modeling the blowout and preparing a kill procedure. The tools of analysis and modeling are limited. In addition, the tools and techniques should be limited to only those absolutely necessary since any wireline operation is potentially critical. With the underground blowout, the condition of the well bore can never be known to a certainty and the risk of sticking or losing wire and tools is significantly increased. Stuck or lost wire and wireline tools limit future operational alternatives. P. 661^

Emergence of Delamination Fractures Around the Casing and Its Stability

“…Similar phenomenon has been observed in faults along dissimilar materials (He, et al,. 1989 and1994). fronts.…”

“…The underground blowout (UGB) is in general characterized by a lack of pressure response on the annulus while pumping on the drill pipe or by a general lack of pressure response while pumping (Grace, et al, 1994). In UGBs, excessive pressure of formation fluid generates excessive stress on the wellbore, which could cause delamination along the interface of casing and cement (or cement and formation) in the weakest parts.…”

“…The broaching of fluid through cement sheath imposes serious challenges to long-term wellbore integrity. These kinds of broaching are usually developed along weaker paths around the wellbore as a result of fluid pressurization, such as hydraulic fracturing and leakage around the casing shoe , Grace, 1994. In order to understand the physical mechanism during the broaching and its influential parameters, it is significant to understand the liquid movements and failure paths around the wellbore.…”