As part of drilling operations, geological information about formation is required to evaluate a reservoir. Coring is a process of taking a sample of reservoir rock for further analysis, to obtain information on reservoir porosity (fluid-carrying capacity), permeability (the ability of fluids to flow) and hydrocarbon and water saturation. Knowing these properties is required to estimate hydrocarbon production and how variation in these parameters will affect production and ultimate recovery.
Coring services consist of the following activities: 1) acquiring core samples of cylindrical shape, 2) preparation for shipment, which includes split into core plugs of up to 3” long each, core plugs stabilization and 3) packing for transportation. Sometimes a coring company will be in charge of transportation to a laboratory as well.
There are four distinct methods that are used to collect core samples:
- Conventional coring - A core bit (similar to the drill bit, but with hollow/empty centre) is placed at the bottom of the drill string, with a core barrel located immediately above the coring bit. The barrel (fibreglass or aluminium) is where the core sample is retained. By rotating the drill string with the coring assembly, a sample rock enters the core barrel where it is protected till it reaches the surface. Typically, inner and outer core barrels, a core catcher and a pressure-relief valve are part of the core barrel assembly. A key advantage of conventional coring is that it allows a larger diameter core sample to be obtained in a single coring operation. The major disadvantage of this technique is the cost because the drill pipe must be removed and replaced with special coring assembly. It works in the same order when coring job is done, i.e. all coring equipment is recovered and drilling tools are run back. As a result, core sampling becomes very costly, when high daily rig and services rates are incurred.
- Diamond Coring - is a conventional coring method whereby a diamond-head core bit is used. Although costing up to 20x more than the conventional core bit, the benefits of using diamond core bit may outweigh the costs and provide significant benefits due to higher penetration rates when coring is dense or hard formations.
- Wire-line coring - is a similar conventional coring process, but coring equipment with additional tools is run on a wire-line inside the drill pipe. Hence, drilling can suspend and start again immediately after the coring job has been completed, making it significantly more cost-effective. This coring technique is used mostly for a wildcat/exploration well, when the depth of coring is not known, before a well is drilled.
- Sidewall Coring tool allows collecting core samples after the well has been drilled and logged. Using wire-line, the tool can be positioned at the exact depth to obtain samples horizontally. While this may be a cost-effective solution in certain cases, conventional coring is still the first choice, as it provides information on the complete geological composition and sequencing of the reservoir rock. Each having its application and limitations, sidewall coring tool could be rotary, percussion and mechanical. During sidewall coring, several (up to 110) small core samples are obtained, 1” in diameter and 2”-3” long.
Risks & Opportunities
Value opportunities and risks are features or requirements that may add or detract from the overall value offered. To ensure value is maximized attention should be given to the following areas:
Personnel Experience and Knowledge - Knowledge / previous experience of reservoirs is of utmost importance to implement a successful coring job
- Availability - Planning ahead
- Quality of Core - Accuracy of core samples, its stabilization and preservation is critical to ensure that the accurate data can be obtained for further interpretation.
Supply & Demand Dynamics
Demand for Coring services driven by exploration and appraisal activities around the world and to a small extent by field redevelopment. Around 95% of coring services are required during the phase of exploration and appraisal. Coring services have been traditionally a small and cyclical market, with the growth highly correlated with exploration activities and oil price.
Due to limited exploration activities in the Middle East and current oil price environment and preference to brownfield projects, coring services would show very limited growth opportunities. In addition, Middle East represents the smallest proportion in this segment, due to major discoveries being made in the last century. Major areas of regional exploration and appraisal activities are the Red Sea, offshore Abu Dhabi and offshore Oman
Due to complexity and cost risk of coring operation, a great deal of planning is required. Knowledge of reservoir is of utmost importance to implement a successful coring job. Hence, service companies who possess knowledge of reservoirs around the world would have a competitive advantage in this segment. Corpro (ALS) has been the market leader for decades with more than 30% of world coring jobs done by Corpro.
Coring services is extremely critical for Buyers, as quality of obtained cores and its stabilization directly impact further reservoir studies and a number high impact decisions. While there is ample number of service companies, experience in dealing in similar reservoirs is important, and not many companies may have it. Due to cyclical nature of the category, opportunities exist to take advantages of downturns and perform required coring jobs.
New Entrants is Low
- Knowledge and experience is difficult to overcome
- Cyclical market
Supplier power is Medium
- Proprietary equipment
- Accumulated knowledge is key
- A competitive environment
- Low switching costs
- High entry barriers
Buyer Power is Medium
- A few providers
- Critical to buyers
- Cyclical demand for services
- Does not exist
Cost & Price Analysis
As a result of industry downturn, prices for coring services have been showing an downward trend on a global basis with price decrease of circa 20%. This segment is highly cyclical on the demand side, as such service providers try to keep the capacity balanced and in times of high demand, prices are going up. In addition, due call-out nature of the coring services, fixed costs are high, which in turn leads to opportunistic pricing strategies by suppliers and high profit margins. In the near term, oil price and reduction in exploration will put pressure on services companies and manufacturers to reduce prices.
Majority of coring equipment is proprietary to service companies. Below are the major cost drivers for coring services.
- Steel prices - directly impacts the cost basis
- Personnel Costs - highly volatile , coring personnel is a very skilled job and lack of highly experienced personnel is always evident. Oil price slump and massive redundancies in the industry may have a limited impact on manpower rates.
Total Cost of Ownership
On average, a coring job is made of 90% equipment costs and 10% personnel costs. However, with rig day rates and drilling spread costs, below is an average distribution of cost of a typical coring job (7 days).
As seen, drilling rig and drilling services represent a much higher percentage that the cost of actual coring services. Hence, a commercial model that clearly captures efficiencies and it validity is vital to derive to the total cost of ownership. Evaluation of lost-in-hole prices for coring equipment plays an important role as well, in the event of failure of a coring job.
Suppliers' quality and experiences is the key areas to consider. Competitive tendering with robust technical evaluation model would provide tremendous benefits, both technical and commercial.
Introducing risk and reward mechanism, whereby service provider performance is rewarded and underperformance in penalized might result in a more efficient coring job.