Onikoyi, Abiola S. (Shell Petroleum Development Company) | Nwabueze, Vincent O. (Shell Petroleum Development Company) | Okoro, Felix O. (Shell Petroleum Development Company) | Ajienka, J.A. (University of Port Harcourt)
Several criteria and strategies have been developed to predict sand failures and to select appropriate sand control methods for improved completion designs and to maximise oil production at moderate unit technical cost. The depth criterion, SPADE equation, Rock Mechanic Equations incorporating Brinell Hardness Number and Unconfined Compressive Strength have been used extensively to predict sand production tendencies and to propose completion types. None of these criteria and strategies has explicitly incorporated the depositional environmental factor that defines the origin of these oil-bearing formations. A recent study aimed to correlate depo-belts and depositional environments to actual sand production using historical data of producing wells in the Niger Delta but covered only the Greater Ughelli depo-belt to some depths (SPE-163010). That study indicated a predominance of high sand producers in the channel sands depositional environment of the Greater Ughelli Depobelt. This paper therefore seeks to complete the investigation across all the remaining depo-belts and litho-facies and to share the review outcomes/ findings with the goal of establishing correlation between known rock mechanic principles and models used in sand failure prediction and sand control selection as a total system approach, providing wider solutions to sand control challenges in the oil industry.
Sand production in oil wells impairs full reservoir production capability, erodes sand face completions, down-hole tubular and surface equipment. The debilitating effects of sand production on surface production equipment are manifested in the plugging of flow lines, production manifolds and separators , leading to significant deferment in production due to downtime of facilities for sand clean out and component repair and replacement.
2000 oil wells in the Niger Delta area have been reviewed to understand the sanding tendencies of the oil well completions and establish the completion strategy and practices that have successfully reduced sand production and its impact. It is observed that over 100 Mbopd oil is locked in as a result of produced sand. A plethora of sand control mechanisms such as Internal Gravel Packs, External Gravel Packs, Stand-Alone Screens, Premium Screens and Sand Consolidation Chemicals have been installed to reduce sand production in oil wells to acceptable rates but several cases of failures have been observed reviewing the past history of the oil wells.
While several operators have developed guidelines to judge when sand control is required and how to operate the oil wells safely, there are still grey areas to be explored to understand the variation of formation consolidation indices from one Depo-Belt to another. The sand production performance of 2000 wells have been reviewed to examine whether the tendency for sanding can be attributed to oil well completion techniques or in-situ formation consolidation or a combination of both. It is also widely believed that formation burial depth can be used as a consolidation parameter to decide whether to include sand control in oil completion design or not.
This paper seeks to share the results of the review of a large population of wells located and completed in different Depo-Belts in the Niger Delta with a view to helping operators streamline their decision-making process to include or not to include sand control systems in their oil wells for efficient production performance at less deferment due to sand production and lower completion and operating cost.