Investigation of asphaltene precipitation in miscible gas injection processes: experimental study and modeling

Abstract

-Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. In this work, static precipitation tests are conducted to investigate the effects of pressure, temperature and gas type and concentration on asphaltene instability. Three different oil samples have been studied under reservoir conditions with/without nitrogen and methane injection. Besides applying common thermodynamic models, a new scaling equation is presented to predict asphaltene precipitation under HPHT gas injection. Extensive published data from the literature are also used in model development. The scaling approach is attractive because it is simple and complex asphaltene properties are not involved in the calculations. Moreover, the proposed model provides universal parameters for different fluid samples over a wide range of pressure and temperature that makes it novel for evaluation of future gas injection projects when simple PVT data are available.

A comprehensive study on mechanism of formation and techniques to diagnose asphaltene structure; molecular and aggregates: a review

“…Natural depletion experiments were carried out by Moradi et al . using three different crude oils with asphaltene content of 0.99, 8.7, and 13.75 wt% . Results show the asphaltene aggregation and precipitation by pressure reduction for crude oils with high‐asphaltene content.…”

Avaliação De Asfaltenos Precipitados Em Diferentes Condições De Composição, Temperatura E Pressão

“…10,[13][14][15][16] Nos petróleos brasileiros são pouco comuns problemas de precipitação de asfaltenos, mas estudos indicam que este fenômeno deve ocorrer nos campos do pré-sal, devido à injeção de CO 2 prevista para esses poços.…”

“…[9][10][11][12] Na prática, uma das razões mais frequentes para a ocorrência desse fenômeno in situ é a injeção de gases (CO 2 , N 2 , hidrocarbonetos leves, gás natural) nos processos de recuperação avançada, ou métodos especiais de recuperação do petróleo. 10,[13][14][15][16] Nos petróleos brasileiros são pouco comuns problemas de precipitação de asfaltenos, mas estudos indicam que este fenômeno deve ocorrer nos campos do pré-sal, devido à injeção de CO 2 prevista para esses poços. 12,17,16 Além de ser um fluido de injeção nos processos de recuperação, o CO 2 é um dos constituintes do gás natural e do próprio petróleo, geralmente presente em concentrações entre traços e 5% (em mol), 18 podendo, contudo, chegar a concentrações mais elevadas, como cerca de 20% (em volume) nos reservatórios do pré-sal.…”

Thermodynamic Analysis and Modeling of Brazilian Crude Oil and Asphaltene Systems: An Experimental Measurement and a Pc-Saft Application

“…Temperature influence on asphaltene solubility is under investigation and different conclusions have been described. Nevertheless, there is a consensus in the literature that the effect of temperature is negligible compared to other parameters such as pressure (Moradi et al, 2012;Verdier et al, 2006). As the asphaltene molecules are quite distinct, depending on the oil origin and the precipitation conditions, it is difficult to characterize them.…”