Influence of the Linear Filtration Law Breach on the Gas-Liquid Mixtures Influx Into the Well

Podkorytova E.O., Skorikov S.D., Smovge A.

Tyumen State Oil and Gas University, Tyumen, Russia

genaevangel@mail.ru

Many practical examples of the well testing (at the Yamburg, Urengoy and other fields in Tyumen) show, that the production curves, by no means always take the shape of a line on the graphs «depression squared – flow rate».

The indicators curves (IC) distortion often occurs not due to the filtration law breach, but due to the fact that a considerable influence of a number of parameters changes that not taken into account: such as super compressibility factor - Z(P,T), viscosity - (P, T), volume factor - B(P, T) and density - (P,T), where P - borehole pressure, T - temperature.

Well known modern methods for this analyzing there date of well testing are not taking consideration the fact that during bilinear, linier and radial filtration gas in fracture and in reservoir may be situations when in the different parts of zones of filtration occurs under the conditions of Darcy’s law breach or not.

The methods for planning and analyzing results of gas well testing, in which early there was realized hydraulic fracture today deal with using methods developed by Gringarten, Cinco-Ley and et. Their methods proposed using type curves and calculations parameters of reservoir by comparing filed curves received during well testing with type curves.

So may be determined as time for realization well testing hydraulic fractured well, so as select adequate model during analyzing process of filtrations.

The influences of all the pointed out factors on the IC and pressure built-up curves (PBU) behavior for hydraulic fractured well is particularly special.

The basic equation used at the analysis of results of gaugings is the Darcy law, which for a radial flow has the form:

ΔР = Pi –Р w = Q•μ/(2•π•k•h) ln (re /rw). (1)

where Pi – initial pressure, P – wellbore pressure, Q – rate, µ - viscosity of gas, k - permeability, h – thickness of layer, re – radius of external, rw – well radius.

As in calculations it is necessary to take into consideration surface gaugings rates for recalculation on wellbore pressure the volume factor.

T he equation (1) precisely enough characterizes process of movement of a liquid in a layer at small depressions. At schedule construction in coordinates as ∆Р – Q, and in coordinates ∆Р2 - Q – curve IC is strongly bent downwards (fig.).

Fig. Examples IC for a case of infringement of the law of a filtration (Darcy)

And only on the schedule (∆Р2)/Q-f (Q) we receive again a straight line, as on fig. The display curve begins not with the beginning of coordinates, and recedes on an axis of abscises on distance equal to A. By this piece (A) probably definition transmissibility a layer.

At the same time, numerous researches of wells as on Urengoj, Yamburg and other reservoir that the real data no means always coincide with the laws accepted here.

Difference is especially striking at research gas condensate deposits.

We must take into account this particularity during interpretation date of well testing.