Abstract

The Hassi-Messaoud field is a low permeability (0.5 - 10 md) average thick sandstone (Cambro-Ordovicien) reservoir covering an area of approximately 2500 km2. It is a flattened anticline and it is located on the north of the El-Biod - HassiMessaoud elevation formed by a sequence of horsts and grabens contained by faults in a submeridiene direction. The faults are in general SSW to NNE oriented and cross all the producing reservoir.

The producing reservoir is at a depth of 11,000 ft and consists of four distinct formations : R3, R2, Ra, in addition to a "zone d'alternance" (transition zone). The Ra is the main producing formation and it is subdivided into five different drains (layers) characterized by distinct petrophysical properties. Overall the field consists of 25 separate zones under pressure maintenance by means of water and/or gas injection. Fig. 1 shows the field different zones and a cross section of the Cambro Ordovicien formation.

Fracturing activities started in the Hassi-Messaoud field in the early sixties as a mean of increasing production. Few massive fractures were performed during the seventies and early eighties. Results were less than satisfactory.

Fracturing activities stopped from 1983 until 1990. This was a period for evaluation and understanding of the results. Activity resumed in 1990 and since over 150 wells have been fractured in the field.

This paper addresses the fracturing activities since it resumed in 1990. It briefly reviews the evolution of fracturing practices. It discusses the existing field limitations and challenges and their effects on fracturing treatment outcome.

An effort is made to match actual job pressures against model. The after fracturing production is presented including efforts to validate post fracture well performance using available pest fractures well tests. Decline rates are grouped in accordance to their severity and the reservoir conformance behavior. Finally, overall conclusions are presented together with recommendations for future treatments.

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