Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. When a real (not ideal) gas expands, the temperature of the gas drops. During passage of a gas through a choke, the internal energy is transferred to kinetic energy with a corresponding reduction in temperature as velocity increases. The effect for natural gas is approximately 7o F for every 100 psi pressure reduction.
While always an implicit goal in steamflood processes, overall process heat management became a topic in the literature in the mid-1980s. The growth of the discipline has closely followed the development of the personal computer and computer applications. Heat management consists of data gathering, data monitoring and adjustments to the process as discussed in this page. Figure 1 is a graphical representation of the major components of a heat balance that must be performed to properly manage a steamflood process. Ziegler et al. published a very good summary of a method of implementing the principle.
Designing a successful steamflooding project requires good candidate selection and an excellent understanding of the mechanisms by which recovery is enhanced. Screening criteria for identification of steamflood candidates have been published for many years. Table 1 shows the screening guides from five different sources. Table 1 - Steamflood project screening criteria It is obvious from Table 1 that there is a finite envelope of properties that define successful candidates. However, within that envelope there is a relatively wide spread of values for the indicators.
Surface facilities for hydraulic pumping systems include a pump at the surface to send the power fluid downhole, a gas, diesel or electric engine to drive the pump, and a system for storing, treating and delivering the power fluid (produced oil or water) for use by the downhole pump. Hydraulic pumping systems have evolved toward the use of relatively high pressures and low flow rates to reduce friction losses and to increase the lift capability and efficiency of the system. Surface operating pressures are generally between 2,000 and 4,000 psi, with the higher pressures used in deeper wells, and power-fluid rates may range from a few hundred to more than 3,000 B/D. While some surface multistage centrifugal pumps are rated to this pressure range, they are generally quite inefficient at the modest flow rates associated with single-well applications. The surface pump for a single well or for just a few wells must be a high-head and low-specific-speed pump.
Rock type influence on permeability discusses how permeability can be significantly affected by rock type, grain size, and extent of compaction or cementation. This page discusses several models that have been developed for estimating permeability based on grain size. Using experimental procedures that were later adopted by Beard and Weyl, Krumbein and Monk measured permeability in sandpacks of constant 40% porosity for specified size and sorting ranges. Although the Krumbein and Monk equation is based on sandpacks of 40% porosity and does not include porosity as a parameter, Beard and Weyl showed that Eq. 1 fits their own data fairly well even though porosity of the Beard and Weyl samples ranges from 23% to 43%. In fact, because of difficulties in obtaining homogeneous sandpacks, Beard and Weyl chose to use computed k values from Eq. 1 rather than their measured data in tabulating values for fine and very fine samples with poor or very poor sorting.
The following discussion of emerging drilling technologies will be limited to those technologies now coming into the market, not those, such as rotary steerable and multilateral technologies, that have ready reference on service company Internet websites. Hence, this discussion is not comprehensive, but it is intended to include most of the high-impact technologies that are likely to be commercialized in the next 3 to 5 years with a brief look beyond. The focus on drilling technology in the United States at the beginning of the 21st century is primarily in response to the fact that its remaining oil and gas resources exist in mature provinces of significantly depleted basins or in difficult drilling environments, such as the Arctic or the deepwater Gulf of Mexico (GOM). Because the United States has led the world in petroleum demand, the environment of depletion and push for further development of these mature basins will provide lessons and technology immediately applicable to the rest of the world as the world resource base continues to mature. All nations have a stake and will benefit from this development of the next redefinition of drilling state of the art.
Disproportionate permeability reduction (DPR) is a phenomenon whereby many water-soluble polymers and many polymer gels reduce the permeability to water flow to a greater extent than to oil or gas flow. DPR is also referred to as relative permeability modification (RPM). In Disproportionate permeability reduction, a review is presented of the concepts, applicability, limitations, and desirability of the DPR phenomenon as it applies to conformance improvement water-shutoff (and/or water-reduction) treatments. This article focuses specifically on polymer use for DPR and RPM. As early as 1964, certain polymer flood water soluble polymers were known to impart DPR to water flow in reservoir rock that had been previously flooded with the polymer.
Over the years, attempts have been made to track the working history of coiled tubing (CT) strings in service to maximize the service utility of the tube while minimizing fatigue failures. As a result, three commonly used methodologies for predicting the fatigue condition of the CT were developed. A relatively simplistic approach used to predict the working life of coil tubing is commonly described as the "running-feet" method, in which the footage of tubing deployed into a wellbore is recorded for each job performed. This deployed footage is then added to the existing record of footage deployed in service for any given string. Depending upon the service environment, type of commonly performed services, and local field history, the CT string is retired when the total number of running feet reaches a predetermined amount.
It is evident that, to quantify formation damage and to study its impact on hydrocarbon production, one must have reasonable estimates of the flow efficiency or skin factor. Several methods have been proposed to evaluate these quantities for oil and gas wells. The most common methods are multirate tests, isochronal gas-well tests, and transient well tests (pressure-buildup analysis). Multirate tests can be conducted on both oil and gas wells. In these tests, several stabilized flow rates, qi, are achieved at corresponding stabilized flowing bottomhole pressures, pwf. The simplest analysis considers two different stabilized rates and pressures. The IPR can be written as ....................(6.6) Simplifying and solving for the flow efficiency, F, we obtain ....................(6.7) The above equation clearly shows that it is possible to obtain flow efficiency rather simply with two stabilized bottomhole pressures and two stabilized flow rates. A similar analysis can be performed to obtain an expression for a linear IPR (x 0). For many gas wells and some oil wells, flow rates are sufficiently high that turbulent or inertial pressure drops near the wellbore can be significant. In such cases, the additional pressure drop measured by the skin can be confused with the pressure drop because of non-Darcy or inertial flow.