While most types of logs are used to characterize the wellbore, formation, and fluids prior to well completion, a number of logging tools are available to provide information during production operations and beyond. This article discusses the various types of production logs and how they can often be used together to provide crucial information for understanding and resolving problems.. Production Logging is one of a number of cased hole services that includes cement monitoring, corrosion monitoring, monitoring of formation fluid contacts (and saturations), perforating and plug and packer setting. Services performed in dead, overbalanced, conditions can use relatively simple surface pressure control equipment and are often performed using large open hole style logging cables. Wells with surface pressure typically have a completion tubing of relatively small internal diameter, ID, compared to the casing size across the reservoir. This reduced ID means that cased hole toolstrings for live wells are typically sized at 1-11/16" in order to pass through the smallest nipple in a 2-3/8" tubing.
Carbon dioxide (CO2) flooding is a process whereby carbon dioxide is injected into an oil reservoir in order to increase output when extracting oil. This project has been completed. It was thoroughly waterflooded before starting miscible injection. This sequence allows a straightforward evaluation of increased recovery because of miscible displacement. Figure 1 shows the oil-production rate for the end of the waterflood and the miscible flood.
Estimating resource and reserves crosses the disciplines between geoscientists and petroleum engineers. While the geoscientist may well have primary responsibility, the engineer must carry the resource and reserve models forward for planning and economics. Volumetric estimates of reserves are among the most common examples of Monte Carlo simulation. Consider the following typical volumetric formula to calculate the gas in place, G, in standard cubic feet. In this formula, there is one component that identifies the prospect, A, while the other factors essentially modify this component.
A production engineer is responsible for generating the production forecast for a well or for a field. Where does the engineer start? Darcy's law gives an estimate of the initial production. Once production drops from the peak or plateau rate, the engineer needs an estimate of decline rate. One can quickly realize that, with all these uncertainties, production forecasts are another candidate on which to use risk analysis techniques to help quantify the uncertainty.
The numbers come from different sources. Take the red jack example. There are 52 cards in a poker deck (excluding the jokers), two of which are red jacks. We simply take the ratio for the probability. Similarly, when we toss two fair coins, we know that there are four outcomes, and we believe that they are "equally likely," for that is indeed what we mean by a fair coin.
Intelligent wells are downhole flow control devices, sensors, power and communication systems, and associated completion equipment. This equipment is used to optimize production, improve recovery, and manage well integrity. Developing an intelligent-completion solution requires the clear definition of well and/or project objectives. Initially flow control devices were based on conventional wireline-operated sliding-sleeve. These valves were reconfigured to be operated by hydraulic, electrical, and/or electrohydraulic control systems to provide on/off and variable position choking.
Since the inception of the technology in the late 1990s, the use of intelligent well technology has focused on production acceleration, increased ultimate recovery, reduced operating expenditure (opex) and reduced project level capital expenditure (capex). The following examples illustrate applications in which this technology has been deployed. Using optimization, the strong lateral is restricted and more chance is giving for the weak one. This cannot be obtained without a downhole valve and surface control in addition to modeling. Objective Achieve production increase based on DTS analysis.
A "well test" is simply a period of time during which the production of the well is measured, either at the well head with portable well test equipment, or in a production facility. Most well tests consist of changing the rate, and observing the change in pressure caused by this change in rate. To perform a well test successfully one must be able to measure the time, the rate, the pressure, and control the rate. A Flow test is an operation on a well designed to demonstrate the existence of moveable petroleum in a reservoir by establishing flow to the surface and/or to provide an indication of the potential productivity of that reservoir. Some flow tests, such as drill stem tests (DSTs), are performed in the open hole.
Managers and engineers alike are concerned about the bottom-line indexes net present value (NPV) and return on investment (ROI) and use these measures to aid in their decision-making, but they also worry about capital requirements and, in our business, reserves. Of course it is the uncertainty in these estimates that makes the "solution" of these problems and making a decision, based on the prediction, so interesting.