The low oil price has forced the industry to take a comprehensive top-to-bottom look at the cost of doing business. The current commodity pricing levels have shown little sign of changing, so companies have had to quickly adjust to the “new normal.” However, “It’s an ill wind that blows nobody good” as E&P companies take advantage of lower seismic data acquisition prices.
Farther down the food chain, the same situation applies with equipment suppliers sharpening their pencils to offer contractors the most competitive deals in a tight market. An obvious and effective short-term way to ease cash outflows is to slash capital spending. From a seismic contractor’s perspective, the most logical steps might be to make do with the recording equipment already in their inventories or to buy the cheapest equipment available. However, while this approach might look like a good short-term decision, focusing on the balance sheet at the expense of the profit-and-loss account could have the medium-term effect of further reducing already thin margins.
Cable vs. cableless
Consider the purchase of a land seismic recording system. In the interests of industry harmony, let’s start by stating that there are no bad systems on the market and each system has its pros and cons, which might make them more suitable to a particular type of acquisition or terrain.
Cable systems can be bought relatively cheaply (the word “relatively” is used advisedly). The systems work well in most situations, but the cables themselves are prone to leakage, especially in wet environments, resulting in considerable time spent at the beginning of each shooting day troubleshooting the cable network. This shortened working day directly reduces crew productivity.
The cables are heavy and bulky, which adds to the cost and complexity of logistics and crew headcount. In populated or agricultural areas where there might be local opposition to exploration, the cables are vulnerable to damage, which further impacts productivity and the operational expenses and costs of cable repairs.
Autonomous nodal systems escape the problems of cables, giving optimal productivity since the contractor can acquire data almost regardless of environmental conditions. These lower weight and volume systems ease logistics and transportation costs. However, some of these gains are reversed by the need to harvest the data, either in situ or at the base camp, both of which require complex transcription and trained staff.
Real-time and cablefree
Wireless Seismic Inc.’s cablefree RT System 2 has a scalable real-time radio network that gives the observer complete control at all times. The system is capable of recording many thousands of channels in real time, just like a traditional cable system. Since it is cablefree, logistics are eased, and since it is a real-time system, there is no complex data harvesting and associated infrastructure or “last patch” effect.
The system transfers data in real time, so it does not require a harvesting function, and it avoids both the “last patch” delay in data availability and the requirement for extra capex on more nodes to compensate for the absence of nodes from the line during data harvesting.
During a recent 3-D survey over varied terrain in the Kurdish Autonomous region of Iraq, a number of advantages of a real-time and cablefree system were demonstrated. The system was deployed in an agricultural area when the fields were being plowed in preparation for sowing. The seismic contractor worked with the farmers to ensure minimal disruption to the crew operations. Because the wireless remote units are free-standing, the farmers were able to plow around them with minimal inconvenience to their plowing schedule (Figure 1). Had the contractor been using a cabled system, the disruption to the contractor and the farmers would have been significant in terms of both lost time and damaged equipment.
Areas of the prospect were steep and rocky, which proved to be a difficult medium in which to consistently plant geophones (Figure 2). The live spread comprised up to 11,000 channels, meaning that 132,000 individual geophones were required to be planted. With the system’s real-time quality control (QC), poor geophone plants were detected instantly across the entire spread. Poorly planted geophones were identified and replanted properly, thus improving data quality. Statistics also can be kept on planting quality for each layout crew.
An earthquake measuring 6.8 on the Richter scale occurred overnight close to the prospect during the survey, with its epicenter over the border in Iran. Aftershocks persisted for 90 seconds every five minutes or so over several days and obliterated the data. There was no physical evidence of the aftershocks at the recorder, but it could be seen clearly on the system’s data displays. Consequently, the crew was able to cease operations as the aftershocks occurred, avoiding acquiring data that otherwise would have been swamped by noise (Figure 3).
At times, there was artillery fire from ISIS and/or Peshmerga forces several miles from the survey area. As with the earthquake aftershocks, the bombardments could not be heard or physically sensed at the recorder or on the line but could be seen distinctly on the data displays. Real-time QC enabled the noise to be monitored and the acquisition suspended and restarted as required (Figure 4).
The lower weight and volume of cablefree systems reduces transportation costs and effort. Contractors using the system consistently enjoy reduced headcount on the crew, with consequent reductions in camp size, the number of vehicles on the crew and the number of vehicle movements, all of which leads to a significant decrease in the headline HSE exposure of the crew. Since the equipment can be redeployed more efficiently because of its high mobility, fewer channels are required on the crew, resulting in a reduction of capital costs.