What is the minimum luminous flux (in ANSI lumens) for a projection
device in order to project readable image on standard screen 1 meter
away in average office illuminance?

The question is a bit vague so let's dispense with any numerical analysis.  

Bear in mind that the level of ambient illumination of the room can
vary by several orders of magnitude in the course of the day, if the
room allows sunlight to enter?

The excess of brightness of the projector above the ambient light
levels determines the maximum contrast ratio the image will present to
the viewer.  The content and complexity of the image will impact
viewers' ability to preceive it accurately at any given contrast
level.

The distance to the viewers affects readibility, as does the darkness
or lightness of the rest of the field of vision around the image
itself (since the viewers' irises will react to this total lighting
level).

All that being said, in my personal experience, just get something in
the 1000 to 2000 lumen range--on loan, and try it at your venue (and
close the curtains).  Be sure it'll focus at the 1 meter distance to
the screen, and that at that distance, the image size is acceptable in
light of the distance to your viewers.

Thanks deeptimer.

I did some research on the projectors and the cheapest were putting
out between 1300 and 1800 lumens but these are comercial projectors
that project on screens some times several meters further. I was
hoping that somebody can provide information that for 1 meter I don't
need more than 1000 lumens.

Where does this 1000 lumen number arise...are you considering a
particular make and model?

1000 lumens projected across just 1 meter is very likely to be just
fine in the usual office situation with normal or modestly subdued
artificial lighting--if it will focus that close (read the datasheet).
 ...But without more details of your room latout, light level, screen
material, etc. and context of use it's impossible to be certain.

At home I'm throwing 2000 lumens onto a 10 foot (diagonal measure)
screen (of "Firehawk" TM material, made by Stewart Filmscreen Corp. in
Burbank CA).  It would be too dim for daytime use, but is terrific for
movies at night.  But my image has much greater total area vs. yours,
over which that light is being spread out.  (Unless you are using an
unusual lens and don't mind geometric distortion (pincushioning) of
the image, your image will be small; perhaps between a third meter to
a meter in diagonal measure, I'd guess.)

Bear in mind that the material used for the screen has a big impact on
apparent image brightness, and has a value referred to as "gain." 
Higher gain screens look brighter by bouncing back the light in a
narrower viewing cone than lower gain screens, so this affects your
seating arrangement.