Mudcake thickness affects wellbore operations such as differential sticking, well completion, and wellbore clean-up operations. One of the properties for which a drilling fluid is screened during laboratory tests is the thickness of the mudcake it produces. Such laboratory tests are routinely conducted on ceramic discs or rock samples, at a specified temperature and pressure. Mathematical models have also been reported for predicting cake thickness and mud induced formation damage. The problem here is that the conditions upon which both laboratory tests and mathematical models are run do not match all conditions in the wellbore during drilling. Calliper tools can be used to directly quantify mudcake thickness in wellbore, however, they cannot differentiate between a sloughing hole and a mudcake. This study therefore explores the potentiality of nuclear magnetic resonance (NMR) logging tools to measure the thickness and porosity of mudcake, and mud induced formation damage in wellbores. This proposed approach utilizes measurements routinely taken from a multi-frequency NMR logging tool, namely T₂ relaxation times at three depth of investigations (DOI). For this specific application, the first DOI captures the mudcake and the near wellbore region, the second DOI captures an inner radius (invaded zone), while the third DOI measures the virgin zone. NMR measurements in these three DOIs were simulated in our laboratory experiments. From the acquired NMR measurements, we identified characteristic T₂ – curves for mudcakes and solid infiltration and then defined a workflow to obtain them. The areas under these characteristic T₂-curves showed good correlations with the mudcake porosity and thickness. Based on these, several calibration curves were developed for mudcake thicknesses, porosity and formation damage. The calibration curves appear to be robust since they were obtained from a variety of rock types with a wide range of porosity and permeability.

泥饼的厚度会影响井眼作业，例如差异压井，完井和井筒清理作业。在实验室测试中筛选出钻井液的特性之一是其产生的泥饼的厚度。此类实验室测试通常在指定的温度和压力下在陶瓷圆盘或岩石样品上进行。还已经报道了数学模型来预测滤饼厚度和泥浆引起的地层破坏。这里的问题在于，进行实验室测试和数学模型的条件与钻井期间井眼中的所有条件都不匹配。卡尺工具可用于直接定量井眼中的泥饼厚度，但是，它们无法区分泥浆孔和泥饼。因此，这项研究探索了利用核磁共振（NMR）测井工具来测量泥饼的厚度和孔隙率以及井筒中泥浆引起的地层损害的潜力。该提议的方法利用了从多频NMR测井仪（即T在三个调查深度（DOI）上有₂次松弛时间。对于此特定应用，第一个DOI捕获泥饼和井眼附近区域，第二个DOI捕获内半径（侵入区），而第三个DOI测量原始区域。在我们的实验室实验中模拟了这三个DOI中的NMR测量。从获得的NMR测量结果中，我们确定了泥饼和固体渗透的特征性T ₂ –曲线，然后定义了获得它们的工作流程。这些特征T ₂下的面积-曲线与泥饼的孔隙率和厚度显示出良好的相关性。基于这些，针对泥饼厚度，孔隙率和地层破坏制定了一些校准曲线。校准曲线似乎是可靠的，因为它们是从具有广泛孔隙率和渗透率的各种岩石类型获得的。