Where isn't it? Oil extraction is a very capital-intensive undertaking, dominated by large corporations and centralized governments, and usually requiring cooperation between the two. Often, the rights, health, and even lives of the local population are ignored, abused or assaulted.
Environmental degradation is usually one of the major problems with drilling and pipeline projects. Contamination of land and water supplies is an immediate threat to human survival.
When the local populace objects strongly enough, the investing corporation might get nervous about the security of their equipment and pipelines, prompting the cooperating government to crack down on the local population in order to maintain the presence of the corporation.
In other cases, the desire to control oil reserves is just another motivating factor for a repressive government...