Taking exploration to a new level

O&G. Maximising the potential of existing oilfields is as much of a challenge as discovering new sources. How can seismic surveying techniques be used to drive more efficient extraction?

AA. Seismic surveys are essential to maximizing field recovery for three reasons, which I will discuss in the order of historical utilization:

1. Depth maps from 3D seismic data provide an accurate image of the structure, or shape, of the field, which indicates to the total volume of the field. Moreover, seismic surveys reveal faults or fracture swarms that may act either as barriers or conduits for fluid movement within the reservoir. This information is important to determine reserves, and the placement and shape of producer or injector wells.

2. Seismic data contains additional information, with attributes such as seismic amplitude or impedance that provide an image of vertical and lateral variations in the quality of the reservoir. The quality parameters include porosity and permeability, which respectively indicate the amount of fluid contained in the rock, and how easily these fluids can flow through the rock. Such information is also important for determining reserves and how to produce them.

3. Furthermore, high fidelity seismic data may also provide an image of the fluid saturation within the reservoir, which refers to the proportion of hydrocarbons to water. This includes direct imaging of hydrocarbon contacts for field delineation purposes, and indirect imaging of hydrocarbon saturation, which are useful for monitoring fluid movement in a time-lapse manner during the production cycle. This time-lapse monitoring is commonly referred to as 4D seismic surveying.

In short, seismic surveys are the principal means for finding the world’s remaining hydrocarbon resources, and are also essential for their efficient extraction. Our reliance on seismic data will actually increase in the future as new technologies and computing horsepower are incorporated. In addition, there are other geophysical techniques, such as electromagnetic and gravity surveys, that are also useful for detecting hydrocarbons in the subsurface.

O&G. Can seismic surveying techniques be used to complement other drilling functions like borehole surveillance to get a more rounded view of reservoirs? If not, is this a challenge that needs to be addressed?

AA. Seismic and well data complement each other for two reasons. First: Seismic and well data have different vertical resolutions or scale. Seismic data can only see relatively thick rock layers, and are incapable of resolving thin layers on the scale of a few meters or less. On the other hand, well data provide higher resolution, on the scale of meters and centimeters. The analogy is that well data are focused on near objects, while seismic data are focused on far objects, and one needs to see both.

Second: Wells are discrete point sources of information around the wellbore, whereas 3D seismic data provide continuous coverage between wells. Once seismic data are calibrated to average reservoir parameters, such as porosity, at the wells, the data can be used to extrapolate these properties away from wells for building computer models of the reservoir.

O&G. Drilling in remote and hostile environments presents may challenges throughout the operation. What are the particular challenges of seismic surveying in these environments?

AA . Both seismic surveys and drilling in remote and hostile environments share many of the same operational challenges, which include safety, security, logistics, and communications. For seismic data acquisition, some areas are obviously challenging such as mountainous terrain or swamps. It is typically more difficult to acquire seismic surveys in congested areas such as cities and producing oil fields. Last, areas of shallow water depth are particularly challenging because large seismic vessels cannot navigate, and seismic acquisition in such areas is therefore slow and expensive.

In addition, some areas are geologically difficult even in settings that are neither remote nor hostile. In such settings, geoscientists are challenged by improving to the quality of seismic data, such as suppression of noise and multiples, modelling of seismic velocity variations, and imaging of thin reservoirs or exploration targets under bodies of salt. These challenges are being overcome through ingenious processing algorithms and faster computers. For drilling, the main challenges are in drilling and evaluating deep wells (over 15,000 feet in total depth). These include mechanical problems such as getting stuck, high temperatures which may exceed the limitations of logging tools, and high pressures which present well control problems.

O&G. How can companies get the most out of 4D surveying?

AA. 4D surveying refers to the practice of acquiring repeat 3D seismic surveys over a producing field for the purpose of monitoring water saturation variation in the reservoir during production. The initial survey should be acquired early, preferably before the onset of production. The biggest challenge in acquiring successive surveys is to exactly re-occupy the locations of sources and receivers used in previous surveys, in order to duplicate the acquisition geometry. This is best accomplished by the installation of permanent seismic monitors. Clearly, getting the most out of 4D surveys requires careful planning and integration with the planning of production facilities.

O&G. Improving the quality of seismic survey data is a constant headache. What new developments do you expect to see in the next five years?

AA. Whereas petroleum geology is a relatively mature science, petroleum geophysics, and particularly seismic technology, is a youthful and rapidly evolving science. I see promise in passive seismic surveying, which uses natural sources of seismic energy within the earth for the direct detection of hydrocarbon accumulations. This holds great promise for exploration, and I expect progress in this technology for determining the type and depth of hydrocarbons in the subsurface. I also expect progress in microseismic technology for mapping fractures in reservoirs and detecting fluid flow through them.

I also expect continued progress in conventional seismic acquisition and processing techniques. In acquisition, the full-azimuth 3D seismic techniques (rich azimuth) have significantly improved imaging in offshore environments. In processing, I expect continued improvements in suppression of noise and multiples, and improved pre-stack depth migration algorithms. In general, I predict major improvements in the analysis of seismic data. These are related to the data-driven wave equation based technology in which the data itself is used to predict multiples, noise and other components of the seismic data. This is a paradigm shift from the rather conventional model-based technologies.

O&G. In your time, what have been some of the key milestones in terms of technology, exploration techniques?

AA. The incredible advances in computing have transformed the way we do things in the geosciences, and substantially improved our productivity. The key milestones were the advent of networked personal workstations, relational databases, parallel processing, and satellite communications. The workstations enabled digital interpretation and mapping of seismic data, as much as word processors replaced the typewriter. Parallel processing replaced large mainframes with greater computing horsepower, which enabled pre-stack processing of seismic data. Satellite communications provided real time transmission of data to the office, which enabled remote geo-steering of directional wells in the reservoir. Relational databases provided instant access of large volumes of data. In addition, other key developments include higher channel seismic crews and global positioning with satellites, which transformed field operations. Other key developments include deep water drilling technologies, logging while drilling, directional drilling, sequence stratigraphy, numerical basin models, and single seismic sensors.

Exploration techniques have not changed much, and continue to rely on seismic surveys for imaging the subsurface. The major improvements in seismic methods followed progress in computing, which enabled pre-stack processing and the creation of more powerful processing algorithms. A key development has been the switch from 2D to 3D seismic surveys for exploration purposes, which started offshore and progressed onshore. Previously, 3D surveys were acquired only over producing fields because they were expensive, particularly on land. Several changes made 3D more affordable, such as increasing number of channels per crew, increasing competition in the seismic industry, and the advent of sparse 3D configurations. Another key development has been the seismic imaging of reservoir porosity and hydrocarbon contacts. In non-seismic methods, the advent of controlled source electromagnetic surveys and gravity gradiometry hold much promise. Having started college with a slide rule, I have been fortunate to have experienced these amazing developments in technology during my career.

O&G. What impact has this had on the industry in terms of going further and deeper for hydrocarbons?

AA. The improvements in computing have substantially improved individual and group productivity, enabling geoscientists to process and interpret larger amounts of data in less time. Improved 3D seismic imaging, particularly under salt, has reduced exploration risk for sub-salt plays, particularly in offshore environments. The improved seismic imaging of reservoir porosity has also reduced exploration risk, allowing the positioning of wells in sweet spots, particularly in deep gas targets. Directional drilling and geo-steering of horizontal wells for field development has greatly improved contact with the reservoir, significantly reducing development cost.

O&G. The Oil & gas industry is facing huge rises in equipment costs. Is this having any effect on your work in geology?

AA. The rise in exploration and field development costs are certainly impacting decisions worldwide, but their impact is somewhat mitigated by revenue from higher oil prices. Most of the increase in exploration costs is due to the increased cost of drilling, which reflect higher rig rates and materials cost. Seismic costs per have also increased due to utilization of greater effort for improved imaging, such as multi and wide azimuth techniques.

We are also seeing higher salaries for skilled geoscientists due to their scarcity worldwide. However, their impact on the economy exceeds that of other highly paid professions, and they deserve all they can get.

O&G. There is a global shortage of skilled labor – problem of recruiting young talent?

AA . There is indeed a shortage of skilled professionals, particularly in the geoscience and petroleum engineering professions. There is a problem in attracting young talent for several reasons: A negative environmental image, uncompetitive compensation in relation to other professions, long-term job instability during boom-bust cycles, and the requirement to relocate far from home. Most high school students perceive geologists as dusty adventurers in the outback , which does not appeal to those inclined towards science and technology. Furthermore, geoscience education at many universities provides inadequate preparation for the industry because the professors have little interest and practical experience. This problem is compounded by the experience gap; because most experienced geoscientists are due to retire within the next 15 years, leaving little time for experience transfer to the incoming generation. This grim situation is improving, but I am afraid too slowly to meet immediate needs.

O&G. The Middle East is now the foremost energy supplier to the world. Do you see this trend changing any time soon?

AA . The Middle East is the world’s leading oil producer with about 30 percent of the world’s daily production, and will remain in the lead for many years to come. This is because of its abundant endowment of conventional oil reserves, estimated at about 750 billion barrels, which corresponds to 60 percent of the world’s total. Furthermore, many geologists estimate that the Middle East contains large amounts of undiscovered petroleum resources that will maintain its leading position well into the future. The position of leading exporter is threatened by the large increase in local energy demand, particularly in the Arabian Gulf region, which will take a bite out of exports. Looking beyond the 20-year horizon, there will be increasing production from unconventional sources such as the Athabasca tar sands, Orinoco heavy oil, and shale. I also expect production from discoveries in new offshore areas, such as the deepwater shelf and Arctic regions.

O&G. And how do you see the Middle East region developing over the next few years with regards to its oil and gas sector? What will be the key issues, challenges and success stories?

AA. The key issues will be the political instability in some countries, the terrorist threat, and the increasing domestic demand for energy, particularly in the Gulf countries. The first challenge for operators is to maintain or increase oil production without negatively impacting the reservoirs. The second challenge is to find additional oil reserves to replace or increase production, particularly through additions from new field discoveries. The third challenge for some countries is to find additional gas reserves to meet domestic and international demand. The fourth challenge is for the industry is to train and retain a new generation of technically skilled workers.

I believe the oil industry in the Middle East will meet these challenges to a large extent. There will be significant oil and gas discoveries in Saudi Arabia, Iraq, Sudan, and Egypt. I also think that Iraq will become a leading energy supplier after it settles down. It is unrealistic to expect the Middle East alone to satisfy the world’s increasing appetite for energy, and there is a definite need to conserve, and develop additional sources of energy.

Abdulkader M. Afifi has over 20 years of experience as a geologist, and is currently Manager of Exploration Technical Services in Saudi Aramco. As well as being President of the Middle East Region for AAPG, he is also a member of the Society of Petroleum Engineers and has served the AAPG as Councilor and International Distinguished Lecturer. Afifi holds a PhD in geology from the University of Michigan, Ann Arbor, and completed the General Management Program at the Harvard Business School. He is married with two daughters.