Applying Risk Analysis to Casing While Drilling

Abstract

TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractEngineers and managers make decisions related to drilling operations every day that must balance the risk of various alternatives. These decisions may be based on a mental, experienced based risk model that has been developed over years of decision making. However, many companies are moving to explicit risk models where risk and its economic impact are quantified. Risk is composed of two components: the probability of an event occurring and the economic consequences if it occurs. This modeling uses a logical progression to predict economic impact of trouble events such as well control, loss of circulation and sticking of the drill string or casing string. Applying a risk model to new technology is difficult because there is no experience base for quantifying either the probability of an event occurring or the consequences of the event. This is particularly true when the technology has operational components that go against normal practices. Such is true with Casing while Drilling. Casing is used as the drill string to solve problems that one would normally expect to be made worse by drilling with a smaller wellbore clearance, higher annular velocity, and little ability to make conditioning trips. This paper will show the results of more than 280 wells and over two million feet of hole drilled with casing over the last eight years. Comparisons will be made to conventional drilling methods in several of the areas where the technology has been applied. Elements of study include casing fatigue, casing wear, tool reliability, underreamer durability and reliability, differential sticking, lost circulation induced by increased ECD, acceptable penetration rates, etc. Results of these wells in difficult drilling areas show positively that drilling with casing is more efficient and encounters less trouble time than conventional drilling, saving operators both time and money. These savings can be seen in daily operating costs, personnel safety and in insurance premiums for the operators and drilling contractors.

Review of casing while drilling technology

“…These wells have been drilled in formations with varying lithology for both offshore and onshore environments. Table 2 below presents a summary of statistics on the retrievable BHAs that have been applied on commercial wells, which were drilled from January 2001 to June 2006 by Tesco Corporation Ltd for vertical and directional applications (Houtchens et al 2007). As shown on Figure 6, the BHA generally consists of a pilot bit and under reamer, but may include other tools needed to perform almost any operation that can be conducted with a conventional drill string.…”

Casing While Drilling

“…Due to difficulties and technological mishaps that may occur during drilling that may increase the wells' final cost, sizeable sums are frequently allotted to achieve such investment plans. However, these sums are frequently wasted before the program is completed [5]. More and more businesses experiment with and use novel drilling techniques and technology that decrease downtime, mitigate risk, and prevent technical mishaps during drilling in an effort to lower such unanticipated expenses of well drilling operations.…”

Análise Probabilística De Estabilidade De Poços De Petróleo

“…O conceito de análise de risco pode ser utilizado em variados cenários a fim de contribuir para a tomada de decisão na engenharia de petróleo e a análise probabilística é uma etapa fundamental ao considerar uma avaliação de risco quantitativa. Murtha (2000) define risco como o potencial de ganho ou perda associados a cada resultado específico, enquanto Houtchens (2007) complementa o conceito afirmando que o risco é uma composição de dois segmentos:…”

“…(ii) As consequências econômicas associadas à ocorrência deste evento. Houtchens (2007) também define a análise de risco como o estudo do risco visando integrar esses segmentos e suas causas, ou seja, uma avaliação que correlaciona os eventos indesejados com suas possíveis causas, sua probabilidade de ocorrência e os gastos associados à sua ocorrência. Gholami et al (2015) utilizam o método de análise quantitativa de risco (QRA) para considerar os efeitos das incertezas associadas aos parâmetros de entrada para a estimativa do cálculo da janela operacional utilizando diferentes critérios de falha.…”