Seat apparatus and method

1. A downhole fracturing system comprising:

a seat assembly having a plurality of like-sized openings therein, each of the like-sized openings having a cross sectional area complementary to a corresponding plurality of objects such that each of the objects is matable therewith to substantially inhibit fluid flow through each like-sized opening, the objects having dimensions insufficient to mate with an opening in a next adjacent upstream seat assembly, wherein a first opening of the plurality of like-sized openings is disposed on a first plane and a second opening of the plurality of like-sized openings is disposed on a second plane off-set of the first plane along an axis extending substantially longitudinally through the seat assembly.

2. The seat apparatus as claimed in claim 1 wherein the seat assembly includes a concave portion operative to guide the objects towards the like-sized openings.

3. The seat apparatus as claimed in claim 1 wherein the like-sized openings are coplanar.

4. The seat apparatus as claimed in claim 1 wherein the objects are spherically shaped.

5. A hydraulic fracturing system, comprising:

a first seat assembly including at least one first opening therethrough having at least one first cross-sectional area, the first seat assembly operatively arranged to receive a first object having a first size greater than the first cross-sectional area while permitting smaller objects to pass through the at least one first opening; and

a second seat assembly positioned downstream of the first seat assembly and having a plurality of second openings, each of the second openings having a second cross-sectional area, the second seat assembly operatively arranged to receive a plurality of second objects each having a second size smaller than the first size, after the second objects have passed through the at least one opening in the first seat assembly, each one of the plurality of second openings corresponding to a corresponding one of the second objects for obstructing fluid flow through the second openings when the second objects are landed at the second seat assembly, wherein a first opening of the plurality of second openings is disposed on a first plane and a second opening of the plurality of second openings is disposed on a second plane off-set of the first plane along an axis extending substantially longitudinally through the second seat assembly.

6. A method of hydraulic fracturing comprising:

dropping a plurality of first objects each having a first size;

landing the plurality of first objects at a first seat assembly, each of the plurality of first objects associated with one of a plurality of first openings in the first seat assembly, wherein a first one of the plurality of first openings is disposed on a first plane and a second one of the plurality of first openings is disposed on a second plane off-set of the first plane along an axis extending substantially longitudinally through the first seat assembly;

obstructing fluid flow through the first seat assembly with the plurality of first objects; and

performing a fracturing operation with fluid upstream of the first seat assembly.

7. The method of claim 6 , wherein dropping the plurality of first objects includes passing the plurality of first objects through at least one second opening in a second seat assembly located upstream of the first seat assembly.

8. The method of claim 7 , further comprising dropping a second object having a second size larger than the first size and landing the second object at the second seat assembly in order to obstruct fluid flow through the second seat assembly.