Definition - What does Unconsolidated Sandstone mean?
An Unconsolidated Sandstone is a rock which contains loosely arranged grains that do not form strong adherence bonds. Sandstone is a detrital sedimentary rock in the category of arenaceous rocks in which the grain size ranges from 1/16 mm to 2 mm in diameter. If hydrocarbons are produced from unconsolidated formations, there are very high chances that sand will also be produced in large quantities along with the hydrocarbons due to the weak bonding.
Petropedia explains Unconsolidated Sandstone
Sandstone is usually dominated by quartz, feldspar and rock fragments which are bound together by a cement of silica, carbonate or a matrix of clay minerals. Sandstone is porous and permeable making it a good reservoir to accumulate producible hydrocarbons.
A sandstone reservoir can either be consolidated or unconsolidated. The difference between the two is that in unconsolidated sandstone, the grain bonding between sand and rocks or stone are loose and do not have a strong bonding between the grains. This makes drilling easy; however, a lot of sand is produced because of loosely packed grains which need to be controlled by implementing sand control procedures. On the other hand consolidated sandstone contains grains that are tightly packed, and thus the production of sand is not that much which is there in the unconsolidated formation, i.e., the sand production during drilling is in a controlled manner.