A modified sub-surface pump is presented with improved gas handling characteristics, and with the ability to flush sand and small particulate matter away from the leading edge of the plunger. The pump design utilizes a tubular hollow valve rod and precision sizing of the guide to create a low pressure chamber above the plunger on the down-stroke.

The two stage gas and sand check valve installed at the top open cage reduces buckling tendency on long stroke down-hole pumps, and actually eliminates the buckling on shorter strokes and shallow wells.

Buckling of valve rods is discussed and a method cf calculating the buckle point for the various plunger and valve rod sizes, and the longer stroke lengths are presented.

The modified hollow valve rod pump with the two stage gas and sand check valve has actually performed in high gas-oil ratio rod pumped wells, under a packer. Brief case histories are discussed in support of the application of this pump to wells where total fluid is produced through the pump.

A review of the basic API pumps with design advantages and disadvantages in down-hole conditions is given. Accessory items to help the basic pumps in handling gas-sand and corrosion are reviewed. These are economical devices, proven over a period of years, that can be readily applied to standard sub-surface pumps.

You can access this article if you purchase or spend a download.