محاسبه‌ي پارامتر هاي ناحيه‌ي آسيب‌ديده‌ي اطراف چاه توليدي با استفاده از آزمون كاهش فشار

Estimation of near well-bore damaged zone parameters from pressure transient data

در اين نوشتار، روشي براي محاسبه‌ي پارامترها ي ناحيه‌ي آسيب‌ديده‌ي اطراف چاه توليدي با استفاده از داده‌هاي فشاري حاصل از آزمون‌ كاهش فشار ارايه شده است. براي اين منظور ابتدا تاثير ويژگي‌هاي ناهمگني تراوايي بر داد ه‌هاي فشاري حاصل از آزمون‌ كاهش فشار شبيه‌سازي شده و با استفاده از روش‌هاي عددي، در يك مخزن مبتني بر مدل مخزن تركيبي بررسي شده است. سپس با در نظر گرفتن مدل مخزن تركيبي براي توضيح مخزن اصلي و محيط آسيب‌ديده‌ي اطراف چاه و با استفاده از نتايج حاصل از بررسي اثر خواص ناهمگني تراوايي بر داده‌هاي فشاري و روابط حاصل از معادلات جريان سيال در مخزن، به محاسبه‌ي تراوايي ناحيه‌ي آسيب‌ديده و شعاع اين ناحيه پرداخته شده است. در انتها نيز روش ارايه شده با استفاده از يك مخزن مصنوعي شبيه‌سازي شده و نيز يك مخزن واقعي صحت‌سنجي شده است.

Estimation of properties of near-wellbore damaged zone made by drilling, completion, injection, and other operations is a challenging issue in reservoir engineering. Researchers have proposed different methods to predict reduction in damaged zone permeability; however, few studies have focused on the prediction of the damaged zone radius and its permeability. In this study, a simple and practical method is proposed to predict the damaged zone properties, i.e., radius and permeability, based on pressure drawdown test data. In this approach, pressure derivative curves for a homogenous reservoir as a base case and a reservoir with spatial permeability variation based on Composite Reservoir model are compared. Eventually, the pressure data points were used for comparison from a drawdown test in a synthetic reservoir model. This spatial permeability variation represents a permeability anomaly. Permeability anomaly makes pressure derivative curve deviate from base curve for corresponding homogenous reservoirs. The parameters of permeability anomaly such as size, orientation, and location have different effects on pressure derivative curve. In reservoir with simple permeability heterogeneity that has a single permeability anomaly, originating location and end location of an anomaly can be predicted by pressure derivative curve. In this study, damaged area radius of a damaged homogeneous reservoir, causing a single anomaly in permeability, is calculated by means of pressure derivative curve, known correlations, and the result from pressure wave propagation concept in reservoir. Short-term pressure data is used to measure the damaged permeability. The method has been validated in a synthetic cylindrical reservoir generated by numerical simulation, as well as in an actual reservoir. For the actual reservoir example, validation is made by comparing the results with Skin Factor model. The proposed method is suggestive of its ability to predict the damaged radius and permeability very well.