The material balance equation is one very important tool to determine OOIP but requires production data and does not give information as to the heterogeneity of the reservoir.
Well Logging could as well be used to determine such information by an indirect method of obtaining the reservoir properties.
You can use the indirect method suggested by Goodness Falayan. The relationship of the reservoir properties which can be derived from well log data are as shown in the doc below.
If you don’t want use the simple methods of MBE or Volumetric concept, use drawdown technique provided the test duration is long enough to reach semi-steady state period.
You can also check "Static reservoir Study" by L. Cosentino.
Cosentino, L. (2005). Static reservoir study. In: Barnaba, P.F., Brighenti, G. and Mazzei, R. (Eds.), Encyclopedia of hydrocarbons, v. I: exploration, production and transport, Chapter no.4 (oil field characteristics and relevant studies). Ente Nazionale Idrocarburi (ENI), Italy, p. 553-573.