Production forecasting decline curve analysis – electricity in human body wiki


There are theoretical equivalent to these decline processes. It can be demonstrated that under conditions such as constant well back pressure, equation of fluid flow through porous media under boundary dominated flow are equivalent to exponential decline. However for our purpose it is the empirical nature of this term which has a greater significance since it allows the technique to be applied to multiple fluid streams even ratios!

Clearly all wells do not exhibit exponential behavior during depletion. In many cases a more gradual hyperbolic decline is observed where rate time performance is better than estimated from exponential solutions implying that hyperbolic decline results from natural and artificial driving energies that slow down pressure depletion. Hyperbolic decline is observed when reservoir drive mechanism is solution gas cap drive, gas cap expansion or water drive. It is also possible where natural drive is supplemented by injection of water gas. electricity usage calculator spreadsheet The type of decline and its characteristic shape is a major feature of DCA. We shall be talking more about this as we go further. gas definition The various types of declines experienced by a well are documented in the Fig 1 and Fig 2.

• Hyperbolic curve fits with a decline constant (b) greater than 1 usually imply production is being influenced by transient behavior. For example b=2 corresponds to transient linear flow and is commonly found with unconventional reservoirs. However, be very careful with these cases – you should build limits into your forecast to capture the eventual transition from transient to boundary dominated flow.

The term ‘b’ has no units and is normally known as hyperbolic constant. Generally ‘b’ can range in value from 0 to 1 in the context of DCA for oil and gas wells. It is evident from Eq 1 that a large value of b ( close to 1) has a dominant effect on shape of the curve q vs. t as t becomes large. This causes and maintains the shape of the curve during this time to be essentially flat. For a given set of values for q and b the short term shape for the curve is not largely effected by the value of b but the long terms shape is. electricity bill payment hyderabad This implies that in short term all decline curves; exponential, hyperbolic and harmonic give similar results. However due the very same reasons make it extremely difficult to determine the value of b. The problem is aggravated if the data is noisy ( which is often the case) making it possible to fit a wide range of b values to the same dataset. electricity symbols worksheet However since the value of b has large impact in the late time, it will lead to different estimates of EUR. Reliability in estimation of b increases with maturity of production data. The value of b captures a large number of physical events and processes. A large body of publications are dedicated to this topic.

The fact that DCA does not have a theoretical basis is an asset here since financial institutions are more acceptable to DCA estimates than other more technical methodologies. A major difference when applying DCA for estimation of reserves arises understandably due the very nature of definitions of reserves and financial implications associated with the process. The ultimate recovery numbers become more important than the profiles. Application of constraints in the production system, operating costs, capital costs and well behavior itself all need to be put into right perspective to come up with reliable estimations.

While everything else remains same, estimation of reserves does come up with several typical situations to which there are no ready answers. electricity bill cost Some of these situations are listed out below for reference. The solutions to these problems could vary from engineer to engineer or organization to organization. Some of the best practices have however been compiled and can be found in production forecasting principles and definition.

Decline analysis and forecasts generated based on such analysis (whether production profiles or reserves) should be fundamentally grounded in good understanding of the factors that control this behavior. ‘No One size fits all ‘ this principal applies truly and universally when it comes to application of DCA. Specifically always arbitrarily using an exponential decline approach for water drive, solution gas drive and gravity drainage systems is neither technically not empirically justified.

Field cases as well as analytical / simulation generally support hyperbolic/harmonic decline for late stage waterflood behavior meaning that value of b lies 0

RF vs. HCPVI, Log (WOR) vs. Np, Log (Qo+Qw) vs. electricity questions and answers physics Np and Masoner plots should be also used in waterflood cases in addition to conventional methods mentioned earlier to ensure estimation of incremental recoveries due to Waterflood and/or impact on recovery due to constraints in the system. As a special case, Roland al (SPE 83470) have proposed techniques to apply DCA on naturally fractured reservoirs that have been developed using waterflooding.

Reservoirs producing with high watercut, high GOR need to be analyzed using ratio plots in conjunction with conventional plots to ensure there is no overestimation of volumes based on rate plots only. (Log WOR vs. Np, Log GOR vs. Np, Watercut vs. c gastritis der antrumschleimhaut Np). Care needs to be taken to understand the minimum criteria for application of these plots. For example Log WOR vs. Cum Oil should only be used if WOR is equal to or higher than 1 ( water cut is equal to higher than 50%).

The DCA technique is most reliable for wells producing at high drawdown against relatively constant flowing pressures, such that the production rate decline mirrors the decline in reservoir pressure. Because of this tie to reservoir pressure, most practitioners restricted its use to the boundary-dominated flow period. However, development of tight and unconventional reservoirs has extended its usage in the transient flow period, necessitating the development of alternative techniques that generally attempt to match the transient and boundary-dominated flow periods using separate parameters. The decline curve treatment offered by Arps was largely applicable to boundary dominated flow (depletion period), whereas Fetkovich focused on the early period of production i.e. transient flow and came up with set of type curves that could be combined with Arps empirical decline curve equation.

The left hand side of Fetkovich type curves are derived from the analytical solution to the flow of a well in the center of a finite circular reservoir producing at a constant wellbore flowing pressure. Fetkovich was able to demonstrate that for all sizes of reservoirs, when transient flow ended, the boundary dominated flow could be represented by an exponential decline as shown below: