Use of a Computer Model in Matching History and Predicting Performance of Low-Permeability Gas Wells
Authors: Joyner Hagan D. , Lovingfoss Warren J. 
Published: December 2007

The performance histories of hundreds of wells in the large, low-permeability Blanco Mesaverde gas field have been matched using a single-well computer model. The task has been accomplished despite some rather adverse factors: a lack of permeability data and stabilized shut-in pressure data for most permeability data and stabilized shut-in pressure data for most of the wells and fluctuating production resulting from proration and workovers.

Introduction
This article is an attempt to share our experience in the use of a single-well computer model in matching history and predicting performance of hundreds of wells in the large, low-permeability Blanco Mesaverde gas field. A lack of permeability data and stabilized shut-in pressure data for most of the wells studied, as well as fluctuating production resulting from proration and workovers, made the study somewhat proration and workovers, made the study somewhat complicated.
The Blanco Mesaverde field is located in the San Juan Basin in northwest New Mexico. The field contains 2,066 wells developed on essentially uniform sparing of one well per 320 acres. The field was discovered in 1926 but significant gas sales did not commence until 1952. Concentrated development began in the early 1950's, and drilling was essentially completed by the late 1950's. The first wells drilled were completed open hole and stimulated with nitro-glycerin. Completion and workover procedure was later changed to open-hole sand-oil hydraulic fracturing and subsequently to cased-hole sand-water hydraulic fracturing using the pseudolimited-entry technique.
The reservoir drive mechanism is gas expansion. The field is produced under proration. During 1970, production was 205.66 Bcf (563 MMcf/D); cumulative production was 205.66 Bcf (563 MMcf/D); cumulative production to Jan. 1, 1971, was 3.006 Tcf. This study production to Jan. 1, 1971, was 3.006 Tcf. This study was made to determine remaining reserves for Continental's interests in the field and to predict the rate of production of these reserves. production of these reserves. Reservoir Characteristics Geology and Rock Properties
The Blanco Mesaverde reservoir is a broad monoclinal stratigraphic trap having productive limits defined by permeability-porosity deterioration. The pay is a heterogeneous sand, shale, and coal section of Lower Cretaceous age. Gross thickness ranges from 400 to 900 ft, and maximum net pay thickness is approximately 200 ft. Average producing depth is 4,542 ft. The Mesaverde is divided into three members, which are designated from top to bottom as the Cliffhouse, Menefee, and Point Lookout (see type log section, Fig. 1). The Point Lookout is the most prolific of the three sand bodies and most of the prolific of the three sand bodies and most of the production and reserves are attributed to this member. production and reserves are attributed to this member. The Cliffhouse is known to be productive in certain areas, but the Menefee is of questionable productivity. The three sand bodies are, for the most part, continuous throughout the field but are heterogeneous both laterally and vertically.
Rock and gas properties are shown in Table 1 These data were obtained from several sources, including information presented to the Federal Power Commission. Cumulative condensate ratio is 3.80 bbl/MMcf, and the current ratio is 4.76 bbl/MMcf.
Porosity is rather uniform, but average per-well permeability varies widely. There is very little permeability varies widely. There is very little permeability data derived from core analyses or pressure permeability data derived from core analyses or pressure tests.
JPT
P. 1415