Performance Analysis of Stimulation Jobs in Multilayered Carbonate Reservoir - A Case Study of Major Offshore Field

Satinder K. Bhatia, Ajay K. Sharma, V. V. Kamat, and S. Chandrasekaran
MH Asset, ONGC Ltd., Mumbai, India

Enhance productivity is the buzz word in today’s high prices of crude oil and therefore maximizing crude oil production from maturing oil field is gaining significance right from spudding of the well. Oil and gas companies have long pioneered the use of drilling technology to achieve greater and greater contact with the reservoir. Selective hydraulic fracturing and stimulation technology has now been added to the arsenal of techniques, introducing a step change to the reservoir contact achievable for each well. The location of reservoir contacts is the predominant concern of asset managers.

Mumbai high field is the giant offshore field in Western India with 1200 sq. Km aerial area. It is the largest and most prolific oil field in India. The field has been divided into two blocks- North and South. It is a limestone reservoir with large scale heterogeneity. There are three main reservoirs viz. L-I, L-II, L-III and S1 (gas bearing). In Mumbai high south field main producing reservoir is L III which in turn is divided into sub layers. Lithology and mineralogy includes Packstones & wacke stones as the prime constituents with patchy dolomatisation. Vugs & channels are the main porosity type with Wide variation in porosity and permeability. Inter layer communication also exists. Shale above & below are not always thick and there is very thin shale layers between the pay layers. Poor cement behind casing is also area of concern. The objective of an oil well stimulation treatment is mainly to improve the connection between the well and the desired reservoir fluids. However, a treatment job can affect the well performance in different ways such as changing the oil rate and reducing the declining rate .To see the entire effect of the stimulation it is necessary to include an important factor i.e. the stimulation job performance as a function of time.

This paper deals with the analysis of stimulation jobs carried out in wells having different completions. In Mumbai high south few wells are completed in single layer and many are conventional and multilayered. The analysis of jobs already carried out will helps us in selecting a suitable job for particular well .

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