Setting heavy cement plugs on top of lighter wellbore fluids is a major problem in Southern Algeria, for both drilling and work-over wells. When setting cement plugs off-bottom, for kick-off or abandonment, an average of 3 attempts are necessary before achieving a competent cement plug. The extra cost of the failed plug operations is around $75,000, plus 4 days of lost rig time. An in-depth analysis of field practices for cement plugs demonstrated that the root cause of the failures is related to poor or non-existent design of the viscous pill rheology. In effect, until recently, the viscous pill was made the same way, regardless of the cement properties and of the cement-viscous pill interface stability. There is a natural tendency for a heavy fluid to fall through a lighter fluid placed below it and it is only by resisting this tendency that cement plugs, set off-bottom, are able to remain static until the cement hardens. The larger the difference in fluid densities or the larger the size of hole, the harder it becomes to stabilize a heavy plug. Commonly, a viscous-pill is set between the cement slurry and drilling mud, in order to improve stability. Recent work, both theoretical and experimental, has determined a reliable estimate of the yield stresses required of the fluids to stabilize an interface separating heavy and light fluids, under any conditions of hole size, deviation and density difference between the fluids. When a viscous pill is used two interfaces: that between the cement slurry and viscous pill and that between the viscous pill and mud, could be unstable. The estimates have been turned into a computer model that can be used to design the physical properties of both viscous pill and cement slurry, so that mechanical stability is ensured. Application of this model to cement plugging operations in Southern Algeria has given rheology and density design targets, which have been applied to both cement slurry and viscous pill. Three case studies are presented in which the top of cement was found exactly as expected, on the first plug set. Over a number of recent cement plug jobs, the success rate has improved from ~25% to close to 100%. Introduction Plugging oil wells is a very common operation. Every well must at some time be abandoned and this usually involves setting cement plugs at several depths. Renewed interest in recovering more oil from well established fields has lead to an increase in sidetracking from existing wells and this commonly requires a cement plug to be set to kick off from. Problems in drilling a new well are also sometimes addressed by using cement plugs, for example to cure lost circulation. Whilst certain plug cementing tasks are viewed as being straightforward, setting cement plugs off-bottom is an operation that is beset with difficulties. Off-bottom plug cementing operations have long1,2 been accepted as a task in which several attempts will be made in order to set a successful plug. An industry average figure for setting cement plugs is frequently quoted as 2.4 attempts per successful plug3,4. However, the failure rate often varies considerably according to local conditions. In Southern Algeria, where the focus of this paper lies, prior to the program adopted by the authors, the average success rate for setting off-bottom plugs was 25%, leading to an average extra cost per plug of $75,000 plus 4 days of lost rig time. Causes of failure have been investigated by several authors3–7 and include the following:Poor mud removalPoorly designed slurry propertiesIncorrect slurry volumePoor temperature estimationPoor job execution and placementInstability of the interfaces and fluid swapping Note that the last of the above problems is only prevalent for off-bottom plugs.

Among all known infectious and tropical diseases in sub-Saharan Africa, malaria is certainly one of the highest in the list of health concerns of African governmental institutions (Table 1) and of oilfield-related companies. Although preventive methods and curative treatment exist, malaria still kills about 2 1/2 million people per year in sub-Saharan African countries. Moreover, in the oilfield industry, a considerable number of nonimmune people travel back and forth between malaria-infested and noninfested areas. Most of the malaria-related fatalities in the oilfield industry come from this type of population. A systematic and methodical approach to malaria prevention was developed and successfully implemented in seven countries in west and southern Africa. In this paper, we explore underlying causes and common patterns seen in malaria fatalities in the oilfield industry using in-depth root cause analysis. Complexity factors are analyzed and their relationship to malaria prevention established, to provide a better understanding of the acuity of the problem. The prevention program is derived from a systematic application of a quality, health, safety, and environment (QHSE) management model. The proposed approach is validated in the short and long term using comprehensive analysis of inputs from a data capturing software. A population of more than 400 nonimmune oilfield personnel traveling in and out of sub-Saharan Africa is used as a sample for the study. It appears that malaria prevention is ineffective if not tackled in a rational manner. Distributing curative and preventive treatment to personnel is not sufficient to solve the problem. Instead, a program based on a logical and structured model, whereby tools and processes are available for each element of the model, provides a more effective approach to malaria risk management to achieve malaria fatality-free operations in west and southern Africa. Introduction Malaria is one of the most important threats to the health of the oilfield population traveling in and out of west and southern Africa. In fact, the most common type of malaria in this part of Africa (malaria P. falciparum or also called cerebral malaria) is life-threatening, and causes 300 to 500 million clinical cases in the world (more than one person is infected every 10 seconds) and more than 2 million deaths occur each year. More than 90% of malaria deaths occur in sub-Saharan Africa (approximately 3,000 deaths each day). Over the past five years, many oilfield industry employees have died from malaria. In almost 100% of the cases, those employees died while on days-off or while traveling outside of the malaria-infested area. Between 2000 and 2002, two major oilfield companies reported six malaria fatalities of their non-African employees and contractors working in west and southern Africa, all happening while outside Africa. In 2002, employees of an oilfield service company reported 16 serious malaria cases in west and southern Africa, most leading to hospitalization. An in-depth analysis and investigation of the above cases have highlighted the following common patterns leading to malaria fatalities:Employees had a "days-off mentality," displaying a higher awareness of the disease on location, but relaxing their vigilance while off location.The incubation period of the disease is from 7 to 60 days.Symptoms of the disease are flu-like and easily confused.Doctors are ignorant of malaria in many parts of the world.Employees displayed a complacent "It won't happen to me" attitude.Curative medication is not available in noninfested areas. In addition to the above, some complexity factors can be added:the notion of semi-immunity against malaria is not well understoodmental barriers to preventive medicationpersonal factors that affect employees behavior with regards to malaria prevention.

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In western and southern Africa, where most sub-Saharan oilfield activity occurs, AIDS is one of the main health concerns of most operators and service companies. Approximately 40 million persons are infected with HIV/AIDS in sub-Saharan Africa. This represents over two-thirds of the worldwide infected population. Although HIV/AIDS is not a work-related disease, most operators and services companies recognize that it affects their workforce and operations. Most oilfield companies aim to recruit and train the vast majority of their work force locally. One barrier to doing so is that, in the oilfield environment, the infection rate and exposure to HIV/AIDS tends to be high due to factors that are analyzed in this paper. Although some oilfield operators have started to implement HIV/AIDS programs, most service companies do not have clear policies and standards for prevention and risk mitigation. In this paper, we review the main factors that contribute to HIV/AIDS risk of infection in oil-producing countries in western and southern Africa. Barriers to prevention are analyzed using a survey of a service company's employees. The survey results are used to determine the extent and the root causes of the problem. Using findings from this study, we outline elements of a prevention program specifically designed for the oilfield work environment. Introduction Sub-Saharan Africa, which represents just over 10% of world population, is estimated to have more than 66% (25 million) of all HIV/AIDS cases, with an infection rate of more than 2 million every year.2 With the increase of the drilling and production activity in this part of the world, oilfield companies in sub-Saharan Africa have started to recognize the impact of this disease. Employees of oilfield companies can be classified into four groups:Married expatriates living with family.Single expatriates.Senior and educated national staff.Junior and uneducated national staff. Single expatriates and national staff are the high-risk groups. It is important to note that contact with HIV/AIDS is exacerbated by the fact that, even for remote projects, ad hoc villages emerge around drilling and production activity. In this environment, key contributing factors for infection are:Lack of an effective HIV/AIDS awareness program.Poverty.Nightlife as one of the main out-of work activities. Many countries in this area are developing economically, and most have suffered years of political and social instability. Therefore, HIV/AIDS prevention has not been a priority. Government programs are nonexistent or are still ineffective. To be effective, any program has to address the following challenges:How much should an oilfield service company be involved?Socio-economic and cultural environment.Traditional and false beliefs about HIV/AIDS.Ignorance or poor understanding of HIV/AIDS.Religious barriers.