A new computer based cementing simulator is described that quantifies the effect of key displacement variables such a s geometry, standoff, fluid rheology and density, and flow rate. The paper shows how to optimise cement placement within the fracture and pore pressure constraints of the well and demonstrates its use through case studies from the North Sea. The technique assesses the quality of mud removal and cement placement as well a s estimating the circulating pressures throughout the job. The examples illustrate how existing rules of thumb can be confusing and how reliable cement jobs can be achieved through quantitative design procedures.
Since the CBL tool came into use over 30 years ago, Bond Index (81) has been the most important parameter in interpreting a valid CBL Log. In recent years, more and more engineers started disbelieving the CBL because they found that eh BI did not often tell the truth. Several investigators have been tackling this problem, but its complexity seems to have been overwhelming. Fundamental studies have been carried out in the BP Research Centre, Sunbury UK. It was found that the BI was obscured by the "engineering treatment" of Attenuation Rates which does not have correct theoretical grounds or physical intuition. This paper analyses BI and its related physical intuition. This paper analyses BI and its related topics, and derives the Bond Percentage Index (BPI) in which is accurate and reliable in predicting the bond conditions. It is concluded that BPI is the correct description of reality and BI, being derived on false basis, should be abandoned. Introduction The Cement Bond Logging (CBL) tool was introduced in the early 60's. It enjoyed two decades in the oil industry without any rivals. From being unable to detect any detail of the cement quality to the CBL must have seemed nothing less than revolutionary. The impact was such that no other tools appeared for another 20 years. Even today the CBL holds the largest market share of any cement evaluation tool, although shortcomings are recognised. The importance of the CBL to the industry is therefore apparent. In recent years there have been some serious attempts to solve some long standing problems associated with the CBL, for example, Jutten et al and Fitzgerald et al. Numerous other papers have been published on the subject. Despite all his work, there are still some key areas where our understanding is inadequate. In this paper we will concentrate on one of such areas: the Bond Index (BI) and related topics. We will attempt to show how some of the earliest papers on the subject have misled more recent workers, resulting in the fundamentally flawed BI and unrelieable CBL practice for 30 years. We will then go on to propose a new Bond Percentage Index which allows a more reliable assessment Percentage Index which allows a more reliable assessment of cement bond quality. So that this paper is self-contained, we will briefly review the CBL principles and history of BI evolution. Comparison of BPI and BI are presented using laboratory results and case studies. Guidelines are then given on how to apply the BPIU to interpretation of field logs.
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