Producing Characteristics and Depositional Environments of Lower Pennsylvanian Reservoirs, Parkway-Empire South Area, Eddy County, New Mexico

ABSTRACT The Parkway-Empire area, on the Northwest shelf of the Permian basin about 15 mi (24 km) northeast of Carlsbad, New Mexico, produces gas from stratigraphic traps within four Lower Pennsylvanian zones: lower and middle Morrow sandstones, Atoka sandstones, and Strawn limestones. The lower Morrow sandstones, which occur at about 11,400 ft (3,470 m), are interpreted to be a prograding fluvial-deltaic sequence of channels and point bars with a northwest source. They trend toward the southeast, generally normal to the Morrowan paleoslope. The lower Morrow sands are separated from the middle Morrow sandstones by a widespread, dark-gray, organic lagoonal shale. In southeastern New Mexico, middle Morrow sandstones are a transgressive series of marine beaches and bars deposited along the northeast-trending ancient shoreline. Stratigraphic traps are created in the lower and middle Morrow sandstones by variations in cementation and depositional patterns. Productive Atoka sandstones occur at approximately 10,700 ft (3,260 m) and appear to be a series of prograding barrier bars deposited along the northeasttrending shoreline. Strawn limestones produce from a series of small, low-relief algal banks developed along northeast depositional strike. The Strawn limestones occur between 10,250 and 10,500 ft (3,120 and 3,200 m). The area is economically attractive. Payout of a typical well occurs in 1.2 years with a rate of return of 78.1%. Pennsylvanian completions in this area have typical ultimate recoveries of approximately 1.5 bcf (42 × 106 m3) of gas and 22,000 bbl (3.5 × 106 L) of condensate. The stacked nature of the reservoirs causes a success rate of 85.2% for this area. The high success rate, good production, and attractive economics make this area of the Morrow trend an important exploration target.