Well construction, well abandonment and restoration of well integrity are the reasons at a broad level why cementing jobs are performed. During well construction phase, the primary objective of cementing job is to replace the drilling mud in the annulus with pure cement. Intermixing of the drilling mud and the cement slurry produces unpumpable mixture, especially in the case of OBM. As literature review suggests the displacement efficiency of spacers and pre-flushes used to displace the drilling mud is not 100%, cement slurries are contaminated with drilling mud left behind the casing. Recently, several research groups have performed studies to understand the strength development phenomenon of OBM contaminated cement slurries, but they failed to document properly the experimental procedures used and correlations for the strength development of OBM contaminated cement slurries.

The primary aim of this study was to develop a standard laboratory experimental procedure for understanding the strength development of OBM contaminated cement slurries and develop correlations for future references. This extensive study was carried out on API Class C cement samples cured at room temperature and elevated temperature. Destructive as well as non-destructive tests were performed on the contaminated as well as uncontaminated cement samples to measure the uniaxial compressive strength (UCS) and the ultrasonic pulse velocity (UPV) respectively. Results obtained from these tests showed deterioration in the strength of cement samples as the OBM contamination increases. Correlations for early strength development of OBM contaminated cement slurries were developed using the test results. These correlations developed would help the operators in better estimation of the strength developed by the OBM contaminated cement slurries. In other words, better estimation of weight on cement (WOC) time using the more accurate strength development correlations.

修井，弃井和恢复井身完整性是进行固井作业的广泛原因。在油井建设阶段，固井工作的主要目标是用纯水泥替代环空中的钻井泥浆。钻井泥浆和水泥浆的混合会产生不可泵送的混合物，尤其是在OBM的情况下。文献回顾表明，用于置换钻井泥浆的垫片和预冲洗液的置换效率不是100％，水泥浆被留在套管后的钻井泥浆污染。最近，几个研究小组进行了研究，以了解被OBM污染的水泥浆的强度发展现象，

这项研究的主要目的是开发一种标准的实验室实验程序，以了解被OBM污染的水泥浆的强度发展，并建立相关性以供将来参考。这项广泛的研究是在室温和高温下固化的API C类水泥样品上进行的。对受污染和未受污染的水泥样品进行破坏性和非破坏性测试，分别测量单轴抗压强度（UCS）和超声脉冲速度（UPV）。从这些测试中获得的结果表明，随着OBM污染的增加，水泥样品的强度会降低。利用测试结果建立了OBM污染水泥浆的早期强度发展的相关性。建立的这些相关性将帮助操作人员更好地估计由OBM污染的水泥浆所产生的强度。换句话说，使用更精确的强度发展相关性，可以更好地估算水泥重量（WOC）。