The methodology section in your academic paper is usually written in the past tense. An explanation of the methods you used in your experience and/or case study is presented in past tense, because this is what you did, in the past. However, scientific methodologies can be written in the future tense, when for example, the experiment has not yet finished and you are unable to record results, your methodology will point towards a future date, with projected results.
If you are writing a psychological or sociological methodology, chances are that you would have processed and analysed the data; hence the methodology will be in the past tense. You are writing your methodology looking back to what you did in your experiments. However, saying this, it is always handy checking your institution’s guidelines for tense use in methodologies, as some will insist on a strict past tense, while others may require the future tense.