Decline curve analysis

Once the production potential of the producing wells is insufficient to maintain the plateau rate, the decline periodbegins. For an individual well in depletion drive, this commences as soon as production starts, and a plateau for the field can only be maintained by drilling more wells. Well performance during the decline period can be estimated by decline curve analysis which assumes that the decline can be described by a mathematical formula. Examples of this would be to assume an exponential decline with 10% decline per annum, or a straight line relationship between the cumulative oil production and the logarithm of the water cut. These assumptions become more robust when based on a fit to measured production data. 

An interwell chemical tracer study established fluid flow patterns within the pilot. Decline curve analysis showed that TFSA injection recovered more than 8150 +... 

Gentry, R. W., 1972, Decline-Curve Analysis Journal of Petroleum Technology, pp. 38—41. 

Oil production from the 10 pilot area producing wells increased from 12 to 95 B/D within eight months after beginning polymer flood operations. Oil production has averaged nearly 100 B/D during the past 22 months which represent a peak oil rate approximately one-third the injection rate (Fig. 7). Cumulative recovery on May 1, 1966, was 243 bbl/acre-ft at a producing water-oil ratio of 0.76. Ultimate pilot recovery is estimated to be 350 bbl/acre-ft after six years flood life. These predictions were made from individual well decline curve analysis and theoretical approaches based on Refs. 3 and 4. 

Hook, M., 2009. Depletion and Decline Curve Analysis in Crude Oil Production. 

Incremental oil production for each of the pilot wells was calculated by subtracting the extrapolated production decline curve which was established prior to TFSA injection from the actual production after TFSA injection. Results of this analysis indicate that a total of 8150 + 850 bbl (1295 + 135 m3) of incremental oil were obtained due to injection of TFSA. 

Analysis of the hyperbolic decline curves indicated that 8150 + 850 bbl (1295 + 135 m3) of incremental 18° API oil were recovered during the 18 month pilot project. 

A simplified analysis of production decline curves was initially intended for evaluation of individual oil well production however, this type of analysis can also provide reasonable estimates when applied to multiple-well LNAPL recovery systems. This analytical method is applicable to most types of decline curves, whether they tend to follow exponential, hyperbolic, or harmonic forms. The following general differential equation is applicable to all forms of decline curves ... 

In Figures 8 and 9 are shown the data for the dependence of the characteristic film buildup time t on Apg and U. In accord with the model, t is found to be independent of U, with only a very weak dependence on Apg indicated. This latter result could in part be a function of experimental inaccuracy. The data reduction for t introduces no assumptions beyond that needed to draw the exponential flux decline curves such as those shown in Figures 2 and 3. However, an error analysis shows that the maximum errors relative to the exponential curve fits occur at the earlier times of the experiment. This is seen in the typical error curve plotted in Figure 10. The error analysis indicates that during the early fouling stage the relatively crude experimental procedure used is not sufficiently accurate or possibly that the assumed flux decline behavior is not exponential at the early times. In any case, it follows that the accuracy of the determination of 6f is greater than that for t. 

An example of a supervised trial model in the Pesticide Agenda is shown in Figure 1, using bifenthrin at the highest recommended dosage on clementines. Application method, dosage, and equipment used are indicated in the information accompanying the decline curve. Five samples of 16 fruits each were collected at 0, 3, 7, 14, and 21 days after application and processed for residue analysis. 

Arps, J. J. 1945. Analysis of Decline Curves. Trans. AIME, 160, 228-247. 

Sampling Interval To be able to perform valid toxicokinetic analysis, it is not only necessary to properly collect samples of appropriate biological fluids, but also to collect a sufficient number of samples at the current intervals. Both of these variables are determined by the nature of the answers sought. Useful parameters in toxico-kinetic studies are Cmax, which is the peak plasma test compound concentration Tmax, which is the time at which the peak plasma test compound concentration occurs, Cmin, which is the plasma test compound concentration immediately before the next dose is administered AUC, which is the area under the plasma test compound concentration-time curve during a dosage interval, and t which is the half-life for the decline of test compound concentrations in plasma. The samples required to obtain these parameters are shown in Table 18.12. Cmin requires one blood sample immediately before a dose is given and provides information on accumulation. If there is no accumulation in plasma, the test compound may not be detected in this sample. 

It is important to remember that lipid oxidation is a dynamic process and that TBARS values reflect only one point in this process. The concentration of TBARS for meat tends to increase over the storage period, reach a maximum value, and then decline. When an unknown sample is presented for analysis, caution must be exercised as the sample s placement on this curve is unknown. 

Pressure on prices has developed for commodity chemicals as technology has diffused ever more rapidly, flattening industry cost curves and impeding differentiation (Fig. 4.1). An analysis of a basket of commodity petrochemicals reveals a real decline in gross margins of 2 percent per annum in the USA. 

Initially, the number of nuclei formed per unit time is expected to increase. As nuleation and growth is assumed to consume the same precursor species, both processes at a given stage will start to compete. The nucleation rate will therefore pass through a maximum in time and then decline, in zeolite synthesis many experimental S-shaped crystallization curves have been observed (16,18). Zdhanov and Samulevich advanced a method for analysis of the nucleation and growth part of such curves (25). 

An inverse floating-rate note, or inverse floater, pays a coupon that increases as general market rates decline. It offers enhanced returns to investors who, in contrast to the market consensus, believe the outlook for bonds is generally positive. These notes are suitable when inflation is low and the yield curve positive, both conditions that would, in a conventional analysis, suggest rising interest rates in the medium term. Inverse floaters may also be appropriate when the yield curve is negative, i.e., inverted, should the investor agree with the market consensus, which would be for lower rates in the medium term. 

The analysis of the assimilation as a function of intercellular COp partial pressure suggests a decline of photosynthetic capacity with increasing salinity. The A (p ) response curves of cotton plant grown under salinity condition showed a marked decline (Data not shown), both in the linear portion at low p and in the saturated region at high p. This would imply that non-stomatal limitations of photosynthesis also occur during salt stress, and they involve both rubisco activity and RuBP regeneration capacity (12). Non-stomatal inhibition of photosynthetic capacity has been reported for several salt sensitive species (2, 3, 6, 18). However, it could be possible that the salt induced depression of A(pi) curves is overestimated to an extent which depends on the distribution of open stomata over the leaf (8). 

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