Frankly I don't see the relationship between Mexican oil production and emmigraion.  If crude production drops, Mexico will cut back on exports way before touching domestic consumption (c.f. Indonesia).

In other words, U.S. economy will suffer before Mexico's.  And the jobs that are bringing Mexicans here (construction, food service, etc.) will be among the first to go.

The Mexican government collects roughly a third of its total annual revenue from PEMEX. Of that, approximately 60 percent comes from Cantarell alone. If the field's production declines   anywhere from 8 to 15 percent a year going forward, you can bet it's going to have an impact on the 40 percent of the Mexican population already living in poverty.

Even if there are fewer jobs available here, that won't prevent a mass exodus to this country by those desparate for work.  

I live on the Arizona/Sonora border. The border fence has increased in size dramatically in the past year or so. From urban centers outwards, troops weld up used military landing strip sections, of corregated, perforated steel approx. 12' tall and 6' wide. These peter out about a mile outside town (leftover landing pads are now used up?), and one sees a collage of ugly steel used parts welded together.

In the arroyos, they lay a thick pad of concrete, and sink 4" X 6" steel posts into it, in an offset pattern which allows runoff and small animals to pass, but which is too close together for humans. And on the wide plains, they augment the 8 strand barbed wire (what's left of it) with steel railroad rails, welded up to stand at sternum level to prevent drive throughs. There is a dirt road on this side, and one on that side, and the Border Patrol tries to shadow the coyotes driving vans packed with people on the other side. And the biggest "improvement" is stadium lighting for several miles (and growing by 1/2 mile at a clip), to light it up and allow agents to track and catch some portion of the immigrants.

I see no evidence of the "triple fence" Congress is talking about.

I figure people will continue to pour through until employment stops growing and this country starts deporting illegals. If there are no jobs, immigrants will stop coming.