Production decline rate

The first set of data is for oil production from 22 wells. A quaternary ammonium salt polymer clay stabilizer was utilized in five of the well treatments. Otherwise the 22 well treatment designs were identical. Use of the clay stabilizer in 5 well treatments resulted in a 131% production increase compared to a 156% increase after stimulation of 17 wells without clay stabilizer. Although the initial overall production response of the five clay stabilizer treated wells was less, the overall production decline rate was 4% per year compared to 16%/yr for the treatments which did not include the clay stabilizing polymer. This decline rate was determined for the period 4 to 24 months after well treatment. It is tempting to speculate that the lower initial production response of the five polymer treated wells was due to the formation of an adsorbed polymer layer which reduced formation permeability (particularly of the Wilcox Formation) significantly. 

Figure 4. Production decline rate for wells in the pilot was best fit by a hyperbolic decline model.

Keywords compressibility, primary-, secondary- and enhanced oil-recovery, drive mechanisms (solution gas-, gas cap-, water-drive), secondary gas cap, first production date, build-up period, plateau period, production decline, water cut, Darcy s law, recovery factor, sweep efficiency, by-passing of oil, residual oil, relative permeability, production forecasts, offtake rate, coning, cusping, horizontal wells, reservoir simulation, material balance, rate dependent processes, pre-drilling. 

Introduction and Commercial Application The production decline period for a field is usually defined as starting once the field production rate falls from its plateau rate. Individual well rates may however drop long before field output falls. This section introduces some of the options that may be available, initially to arrest production decline, and subsequently to manage decline in the most cost effective manner. 

As the natural pressures in the reservoir decrease, oil production declines. The oil well may then be placed on-pump to maintain production at economic levels. The pump draws oil to the surface and lowers the height of the fluid column ia the wellbore. The pressure of a column of fluid can decrease the rate of fluid entry into the wellbore. 

Domestic lead metal production rose at an annual rate of 1.3% between 1990 and 1996, going from 1.33 million metric tons to a record high of 1.43 million metric tons. Primary lead production declined at an annual average rate of 3.2% during this time period, dropping from 404,000 metric tons in 1990 to... 

Andre et al. [8] discuss the determination of adenosine-5 -triphosphate by luciferin-luciferase assay. This method was applied to the determination of adenosine-5 -triphosphate in bacterial colonies filtered from samples of polluted water after incubation for different periods. The adenosine-5 -triphosphate was extracted from the residue in the filter and the amount compared with the biochemical oxygen demand of the filtered water. The oxygen uptake rate and the rate of formation of adenosine-5 -triphosphate were then plotted against time, the two curves being similar in up to three to four days incubation, after which adenosine-5 -triphosphate production declined markedly, although oxygen uptake continued to increase. 

The recovery factor is defined as the ratio of additional steam provided by injection to the amount of water injected over the same period of time. Additional steam is the steam produced at the new decline rate (or improvement rate) due to injection minus the steam production calculated at a decline rate without re-injection. The recovery factor defined on the basis of production data may be different from that defined on the basis of geochemical data if considered on a well-by-well basis. However, the combined recovery from all production wells affected by one or more injection wells should agree when applying both methods given sufficient time, since (1) the total amount of boil water should appear as steam in production wells and be reflected in the production data, and (2) the steam originally to be produced from a given well but replaced by injection-derived steam should eventually be produced in other wells. 

Recovery factor calculations may not be possible under certain situations, including (1) a decrease in steam flow rate due to water breakthrough (2) scale deposits in the well-bore and/or fracture conduits (3) a fluctuating flow rate and (4) the completion of additional production wells in injection-affected areas, which will have an impact on the decline rates of nearby production wells. 

When Pt/Ti02 powder is coated with NaOH and illuminated in the presence of gas-phase water, H2 and 02 are produced in a stoichiometric ratio of 2 1 even in the dry state.9,13) Rh and Pd loaded Ti02 powders also show photocatalytic activity for gas-phase water photolysis when coated with NaOH.14) The product formation rates decline with time due to the reverse reaction. The yield of gas-phase water photolysis depends on the pressure of gas-phase water, as shown in Fig. 13.4,14) Since the yield is also dependent upon the amount of NaOH coated,... 

From the temporal scale of adverse effects we come to a consideration of recovery. Recovery is the rate and extent of return of a population or community to a condition that existed before the introduction of a stressor. Because ecosystems are dynamic and even under natural conditions are constantly changing in response to changes in the physical environment (weather, natural catastrophes, etc.) or other factors, it is unrealistic to expect that a system will remain static at some level or return to exactly the same state that it was before it was disturbed. Thus the attributes of a recovered system must be carefully defined. Examples might include productivity declines in an eutrophic system, re-establishment of a species at a particular density, species recolonization of a damaged habitat, or the restoration of health of diseased organisms. 

Batch distillation (Fig. 16) is often preferable to continuous distillation when small quantities of feed material are processed. A liquid feed is charged to a still pot and heated until vaporization occurs. Vapor leaves the top of the column, and after condensation, part is removed as product and the rest returned to the column as reflux. As distillation proceeds, the contents of the still pot and the overhead product become richer in less volatile components. When operated at a fixed reflux ratio, an overhead product cut is collected until the product composition becomes unaccceptable. As an alternative, the reflux ratio can be gradually increased to hold the product composition constant as the cut is taken. For a fixed rate of heat addition to the still pot, the latter option results in a steadily declining product flow rate. After the first cut, subsequent... 

Stage IV Declining Rate. Definition. The declining rate stage is defined as a period of decreasing rate of reaction which tends to approach a limit in the amount of reactant consumed, or product produced (zero rate), under the prevailing conditions of temperautre, irradiance, partial pressure of oxygen, concentration of reactants, etc. 

With a freshly sharpened stone, the produetion rate is high and energy consumption low, but the grits cut the fibres and pulp quality is poor. As the grits wear production declines, there is less eutting, energy demand inereases and pulp quality improves. The pulpmill adjusts the sharpening eyele (about 10 days) of individual stones so that mill pulp quality is approximately eonstant. 

The production of asphalt has increased greatly as the amount of crude oil processed has risen to meet growing demands for petroleum fuels and petrochemicals. From 1925 to 1950, the annual rate of production doubled each decade. After 1950, the rate of growth of asphalt production declined. In 1960, the annual rate was 180% that of 1950, and in 1970, the annual rate was 140% that of 1960. 

Solids production from these heavy oil reservoirs was first discussed in some detail by Smith (97). Smith developed an analytical model to predict production, decline, recovery, pressure, and pressure-transient behavior, together with the large solids volume production and its effect on oil rate and well productivity. Smith s model incorporated time-de-pendent properties of the oil as a result of gas evolution and treated the unconsolidated reservoir sand as a soil in which cohesion relies only on the tension of the wetting phase. This is a similar, though simpler, approach than Vaziri s (54) finite element method. Smith developed a Darcy law formulation for compressible fluid flow... 

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