Production improvement may be summarized as the delivering of incremental productivity by applying a systematic approach that turns problems into opportunities.

The challenge of satisfying the constantly increasing demand for energy drives the oil and gas industry to continue to explore and develop resources. Today's perception is that the world's production capacity has crested as a result of the lack of large discoveries. Large amounts of reserves are, however, still in the ground. This leads to a critical focus on brownfield developments, maturing assets, marginal plays and associated strategies to arrest the decline in the world's producing assets. Successful solutions will need to focus on improving the deliverability efficiency from producing systems and on improving recovery efficiency.
As previously published, in the next 2 decades no more than 10% to 20% of the oil supply, and 30% to 50% of the gas supply, will come from new discoveries in un-exploited areas. This means that more than 50% of the world's total energy supply going forward will have to come from oil and gas from mature areas and unconventional sources.
Accordingly, more and more hydrocarbon production must be wrested from underdeveloped assets and under-producing wells. These are, typically, a result of a lack of practical expertise, technical "know-how," manpower, or alternatively, economic decisions. Whatever the reason, it is safe to say that very few wells are producing today at their optimum capacity. What is, therefore, the solution to sustaining production?
Performance optimization
Production improvement deals with increasing well deliverability and/or enhancing field performance. Optimization, on the other hand, does not necessarily mean selecting and implementing the cheapest option (Figure 1). Saving money is not the key
to optimization. Neither is it blindly choosing the most sophisticated one, turning every well into a science project makes the cost prohibitive and technology impractical. Good judgment must be used in applying a different technology or doing additional analysis while discerning when and how to apply the right technology. The rule should be: if it does not increase production, it is not effective and it does not work.
The following measures are offered for use in the decision-making process:
1. Compare the basic cost;
2. Evaluate the cost in terms of expenditures - $/bbl or $/mcf;
3. Compare the cost-benefit, i.e. efficiency of investment; and
4. Make a timely decision.
The best (or optimized) option:
• Delivers the hydrocarbons at the cheapest unit cost;
• Maximizes production; and
• Provides the optimum return on investment.
In maturing assets, whether they are conventional or unconventional resources, understanding the reservoir through proper diagnostics and knowing what can be achieved with technology is absolutely critical to increasing the productivity and maximizing cost efficiencies. Table 1 suggests a few systematic steps to field optimization.
Field optimization
Performance improvement is only effective on a field-wide multiwell basis. Repeatability and sustainability are important deliverables in a performance optimization program. The objective is simple, to close the gap between the current production and the reservoir potential or technical producing limit for multiwell systems. This can be achieved when one considers that in maturing assets, few wells are producing today at their optimum capacity. Close the gap frequently and this becomes the basis of field optimization. Proactively monitor and act based on selected engineering diagnostics and efficiency improvement and this will form the foundation for real-time optimization.
A multiwell system optimization targets the reservoir diagnostics and the deliverability efficiency, providing a ranking for implementation based on the efficiency of investment.
Figure 2 illustrates the ranking of opportunities for intervention based on financial performance. For an operator with a well stock of 130 wells, it was identified that 250 fracture stimulation treatments will address reserves behind pipe through pin-point fracture stimulation (additional pay and picking up incremental kh), 30% of the wells were identified as re-fracturing candidates. Assumptions were made in terms of operational efficiency, net gas price, treatments costs, operating costs, technical limits and deliverability efficiency of the reservoir-completion. The financial analysis demonstrated that the optimum approach was to implement the top 102 interventions. Figure 2a presents the ranking of opportunities for the analyzed well stock based on the deliverability uplift (incremental Dqgas), Figure 2b illustrates the optimum number of interventions to be executed, and Figure 2c presents the financial ranking criteria based on the efficiency of investment. This provides a practical strategy suitable for the optimization of fields with significant production history (old and new fields, brownfields, mature and marginal fields).
Tools
A wide spectrum of tools is available for use during the optimization process, from spreadsheet-based analysis to fit-for-purpose software products. In practice, one needs to identify the level of complexity of the problem at hand and match the tool accordingly. Following are areas where software tools are readily available off-the-shelf.
Reservoir description. This entails the understanding of the reservoir, particularly in the near wellbore region and is accomplished via the analysis of well logs that deliver the variation of specific reservoir parameters like porosity and water saturation along the length of the well. Measuring the variation in pressure in shut-in and flowing wells (Pressure Transient Analysis) is a common way to determine such critical parameters as reservoir permeability.
Production analysis. The objective is to quantify the reservoir parameters and the efficiency of the well completion and confirm the deliverability of the well.
Predictive capacity. After addressing any problem conditions, the next step is to forecast the future performance. This may be accomplished via single-well modeling or analytical solutions.
What-if scenarios. The objective is to conduct sensitivity analysis on various parameters assessing their impact on performance.
Economics. The financial impact of changes or actions to be taken can be assessed at this stage of the analysis.
Production rates and surface pressure readouts are usually the most common source of data. It makes sense then to utilize rate transient analysis, material balance and Nodal Analysis.
The approach
There are three common peculiarities that one finds among operators of maturing fields around the world. These are:
1. I need more data. The first action operators want to take is to acquire more data. However, they should ask:
• Has all the information relative to these fields been interpreted, analyzed and understood?
• Is there a real necessity for 100% of the data?
• How much information is needed before making a decision?
In the meantime no decision leads to inaction that translates into loss of production. A production optimization philosophy should be one of analysis conducive to action, where all information is systematically reviewed, analyzed and acted upon.
2. Let's deal with the problems rather than create opportunities. When facing a production enhancement initiative, many operators tend to bring out the problem wells, "make a gusher out of a dog-well." All the focus is on problems rather than on trying to create a production increment. Take for example two similar wells in the same field. Well "A" produces 20 bbl while well "B" producing 300 bbl, is the "good" well. Typically most of the efforts are towards increasing production from well "A" while well "B" will never be touched. A true optimization way of thinking will try to improve the production from well "B" i.e. turn good wells into better wells. If production increases by 30%, this will mean an incremental q of 6 and 90 bbl for well "A" and "B," respectively. The decision-making process then becomes - if we can estimate the potential and we believe in our engineering analysis, then why settle for less when the estimated reservoir potential tells us that the gap is substantial?
3. Let's focus on other issues. As a result, the priorities move away from engineering and focus on chasing rigs, following the drilling operations, managing contracts and the daily operations. These have little relevance to field production optimization.
To counteract these three prevalent characteristics, the challenge of optimizing maturing assets requires:
• Well-founded engineering;
• Know-how;
• Experience;
• A good dose of innovation;
• Decision-making capability;
• Technical leadership; and
• A credo of production improvement via an opportunity creation process.
Closure
If the reservoir is not depleted, has the potential, reserves and available pressure the decision should be to proceed with interpretation and analysis. The knowledge, the tools and the technology are here. The challenge, and the time, for production improvement is now.

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